90ba33099c
This patch canonicalizes getelementptr instructions with constant indices to use the `i8` source element type. This makes it easier for optimizations to recognize that two GEPs are identical, because they don't need to see past many different ways to express the same offset. This is a first step towards https://discourse.llvm.org/t/rfc-replacing-getelementptr-with-ptradd/68699. This is limited to constant GEPs only for now, as they have a clear canonical form, while we're not yet sure how exactly to deal with variable indices. The test llvm/test/Transforms/PhaseOrdering/switch_with_geps.ll gives two representative examples of the kind of optimization improvement we expect from this change. In the first test SimplifyCFG can now realize that all switch branches are actually the same. In the second test it can convert it into simple arithmetic. These are representative of common optimization failures we see in Rust. Fixes https://github.com/llvm/llvm-project/issues/69841.
189 lines
6.8 KiB
LLVM
189 lines
6.8 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -S -passes=instcombine < %s | FileCheck %s
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; Check that we don't create two redundant phi nodes when %val is used in a
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; form where we can't rewrite it in terms of the new phi node.
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; Use %val in an instruction type not supported by optimizeBitCastFromPhi.
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define float @sitofp(float %x) {
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; CHECK-LABEL: @sitofp(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[LOOP_HEADER:%.*]]
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; CHECK: loop_header:
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; CHECK-NEXT: [[VAL:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[VAL_INCR_CASTED:%.*]], [[LOOP:%.*]] ]
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; CHECK-NEXT: [[VAL_CASTED:%.*]] = bitcast i32 [[VAL]] to float
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; CHECK-NEXT: [[CMP:%.*]] = fcmp ogt float [[VAL_CASTED]], [[X:%.*]]
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; CHECK-NEXT: br i1 [[CMP]], label [[END:%.*]], label [[LOOP]]
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; CHECK: loop:
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; CHECK-NEXT: [[VAL_INCR:%.*]] = fadd float [[VAL_CASTED]], 1.000000e+00
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; CHECK-NEXT: [[VAL_INCR_CASTED]] = bitcast float [[VAL_INCR]] to i32
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; CHECK-NEXT: br label [[LOOP_HEADER]]
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; CHECK: end:
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; CHECK-NEXT: [[RESULT:%.*]] = sitofp i32 [[VAL]] to float
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; CHECK-NEXT: ret float [[RESULT]]
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;
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entry:
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br label %loop_header
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loop_header:
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%val = phi i32 [ 0, %entry ], [ %val_incr_casted, %loop ]
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%val_casted = bitcast i32 %val to float
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%cmp = fcmp ogt float %val_casted, %x
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br i1 %cmp, label %end, label %loop
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loop:
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%val_incr = fadd float %val_casted, 1.0
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%val_incr_casted = bitcast float %val_incr to i32
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br label %loop_header
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end:
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%result = sitofp i32 %val to float
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ret float %result
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}
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; Use %val in an incompatible bitcast.
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define <2 x i16> @bitcast(float %x) {
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; CHECK-LABEL: @bitcast(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[LOOP_HEADER:%.*]]
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; CHECK: loop_header:
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; CHECK-NEXT: [[VAL:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[VAL_INCR_CASTED:%.*]], [[LOOP:%.*]] ]
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; CHECK-NEXT: [[VAL_CASTED:%.*]] = bitcast i32 [[VAL]] to float
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; CHECK-NEXT: [[CMP:%.*]] = fcmp ogt float [[VAL_CASTED]], [[X:%.*]]
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; CHECK-NEXT: br i1 [[CMP]], label [[END:%.*]], label [[LOOP]]
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; CHECK: loop:
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; CHECK-NEXT: [[VAL_INCR:%.*]] = fadd float [[VAL_CASTED]], 1.000000e+00
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; CHECK-NEXT: [[VAL_INCR_CASTED]] = bitcast float [[VAL_INCR]] to i32
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; CHECK-NEXT: br label [[LOOP_HEADER]]
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; CHECK: end:
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; CHECK-NEXT: [[RESULT:%.*]] = bitcast i32 [[VAL]] to <2 x i16>
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; CHECK-NEXT: ret <2 x i16> [[RESULT]]
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;
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entry:
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br label %loop_header
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loop_header:
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%val = phi i32 [ 0, %entry ], [ %val_incr_casted, %loop ]
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%val_casted = bitcast i32 %val to float
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%cmp = fcmp ogt float %val_casted, %x
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br i1 %cmp, label %end, label %loop
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loop:
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%val_incr = fadd float %val_casted, 1.0
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%val_incr_casted = bitcast float %val_incr to i32
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br label %loop_header
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end:
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%result = bitcast i32 %val to <2 x i16>
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ret <2 x i16> %result
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}
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@global = global i32 0
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; Use %val with a volatile store.
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define void @store_volatile(float %x) {
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; CHECK-LABEL: @store_volatile(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[LOOP_HEADER:%.*]]
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; CHECK: loop_header:
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; CHECK-NEXT: [[VAL:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[VAL_INCR_CASTED:%.*]], [[LOOP:%.*]] ]
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; CHECK-NEXT: [[VAL_CASTED:%.*]] = bitcast i32 [[VAL]] to float
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; CHECK-NEXT: [[CMP:%.*]] = fcmp ogt float [[VAL_CASTED]], [[X:%.*]]
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; CHECK-NEXT: br i1 [[CMP]], label [[END:%.*]], label [[LOOP]]
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; CHECK: loop:
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; CHECK-NEXT: [[VAL_INCR:%.*]] = fadd float [[VAL_CASTED]], 1.000000e+00
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; CHECK-NEXT: [[VAL_INCR_CASTED]] = bitcast float [[VAL_INCR]] to i32
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; CHECK-NEXT: br label [[LOOP_HEADER]]
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; CHECK: end:
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; CHECK-NEXT: store volatile i32 [[VAL]], ptr @global, align 4
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; CHECK-NEXT: ret void
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;
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entry:
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br label %loop_header
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loop_header:
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%val = phi i32 [ 0, %entry ], [ %val_incr_casted, %loop ]
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%val_casted = bitcast i32 %val to float
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%cmp = fcmp ogt float %val_casted, %x
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br i1 %cmp, label %end, label %loop
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loop:
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%val_incr = fadd float %val_casted, 1.0
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%val_incr_casted = bitcast float %val_incr to i32
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br label %loop_header
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end:
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store volatile i32 %val, ptr @global
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ret void
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}
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; Use %val with a store where it's actually the address.
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define void @store_address(i32 %x) {
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; CHECK-LABEL: @store_address(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[LOOP_HEADER:%.*]]
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; CHECK: loop_header:
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; CHECK-NEXT: [[VAL:%.*]] = phi ptr [ @global, [[ENTRY:%.*]] ], [ [[VAL_INCR:%.*]], [[LOOP:%.*]] ]
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; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 0
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; CHECK-NEXT: br i1 [[CMP]], label [[END:%.*]], label [[LOOP]]
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; CHECK: loop:
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; CHECK-NEXT: [[VAL_INCR]] = getelementptr i8, ptr [[VAL]], i64 4
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; CHECK-NEXT: br label [[LOOP_HEADER]]
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; CHECK: end:
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; CHECK-NEXT: store i32 0, ptr [[VAL]], align 4
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; CHECK-NEXT: ret void
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;
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entry:
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br label %loop_header
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loop_header:
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%val = phi ptr [ @global, %entry ], [ %val_incr, %loop ]
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%i = phi i32 [ 0, %entry ], [ %i_incr, %loop ]
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%cmp = icmp sgt i32 %i, %x
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br i1 %cmp, label %end, label %loop
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loop:
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%i_incr = add i32 %i, 0
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%val_incr = getelementptr float, ptr %val, i32 1
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br label %loop_header
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end:
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store i32 0, ptr %val
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ret void
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}
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; Test where a phi (%val2) other than the original one (%val) has an
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; incompatible use.
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define i32 @multiple_phis(float %x) {
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; CHECK-LABEL: @multiple_phis(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[LOOP_HEADER:%.*]]
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; CHECK: loop_header:
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; CHECK-NEXT: [[VAL:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[VAL2:%.*]], [[LOOP_END:%.*]] ]
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; CHECK-NEXT: [[VAL_CASTED:%.*]] = bitcast i32 [[VAL]] to float
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; CHECK-NEXT: [[CMP:%.*]] = fcmp ogt float [[VAL_CASTED]], [[X:%.*]]
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; CHECK-NEXT: br i1 [[CMP]], label [[END:%.*]], label [[LOOP:%.*]]
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; CHECK: loop:
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; CHECK-NEXT: [[CMP2:%.*]] = fcmp ogt float [[VAL_CASTED]], 2.000000e+00
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; CHECK-NEXT: br i1 [[CMP2]], label [[IF:%.*]], label [[LOOP_END]]
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; CHECK: if:
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; CHECK-NEXT: [[VAL_INCR:%.*]] = fadd float [[VAL_CASTED]], 1.000000e+00
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; CHECK-NEXT: [[VAL_INCR_CASTED:%.*]] = bitcast float [[VAL_INCR]] to i32
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; CHECK-NEXT: br label [[LOOP_END]]
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; CHECK: loop_end:
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; CHECK-NEXT: [[VAL2]] = phi i32 [ [[VAL]], [[LOOP]] ], [ [[VAL_INCR_CASTED]], [[IF]] ]
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; CHECK-NEXT: store volatile i32 [[VAL2]], ptr @global, align 4
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; CHECK-NEXT: br label [[LOOP_HEADER]]
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; CHECK: end:
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; CHECK-NEXT: ret i32 [[VAL]]
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;
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entry:
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br label %loop_header
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loop_header:
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%val = phi i32 [ 0, %entry ], [ %val2, %loop_end ]
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%val_casted = bitcast i32 %val to float
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%cmp = fcmp ogt float %val_casted, %x
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br i1 %cmp, label %end, label %loop
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loop:
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%cmp2 = fcmp ogt float %val_casted, 2.0
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br i1 %cmp2, label %if, label %loop_end
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if:
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%val_incr = fadd float %val_casted, 1.0
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%val_incr_casted = bitcast float %val_incr to i32
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br label %loop_end
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loop_end:
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%val2 = phi i32 [ %val, %loop ], [ %val_incr_casted, %if ]
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store volatile i32 %val2, ptr @global ; the incompatible use
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br label %loop_header
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end:
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ret i32 %val
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}
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