0be0a1237c
This is based on the example/comments in: https://llvm.org/PR48984 I tried just lifting the restriction in computeKnownBitsFromShiftOperator() as suggested in the bug report, but that doesn't catch all of the cases shown here. I didn't step through to see exactly why that happened. But it seems like a reasonable compromise to cheaply check the special-case of shifting a constant. There's a slight regression on a cmp transform as noted, but this is likely the more important/common pattern, so we can fix that icmp pattern later if needed. Differential Revision: https://reviews.llvm.org/D95959
103 lines
3.3 KiB
LLVM
103 lines
3.3 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -instcombine -S | FileCheck %s
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; Remove an icmp by using its operand in the subsequent logic directly.
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define i8 @zext_or_icmp_icmp(i8 %a, i8 %b) {
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; CHECK-LABEL: @zext_or_icmp_icmp(
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; CHECK-NEXT: [[MASK:%.*]] = and i8 [[A:%.*]], 1
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; CHECK-NEXT: [[TOBOOL2:%.*]] = icmp eq i8 [[B:%.*]], 0
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; CHECK-NEXT: [[TOBOOL22:%.*]] = zext i1 [[TOBOOL2]] to i8
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; CHECK-NEXT: [[TMP1:%.*]] = xor i8 [[MASK]], 1
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; CHECK-NEXT: [[ZEXT3:%.*]] = or i8 [[TMP1]], [[TOBOOL22]]
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; CHECK-NEXT: ret i8 [[ZEXT3]]
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;
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%mask = and i8 %a, 1
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%toBool1 = icmp eq i8 %mask, 0
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%toBool2 = icmp eq i8 %b, 0
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%bothCond = or i1 %toBool1, %toBool2
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%zext = zext i1 %bothCond to i8
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ret i8 %zext
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}
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define i8 @zext_or_icmp_icmp_logical(i8 %a, i8 %b) {
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; CHECK-LABEL: @zext_or_icmp_icmp_logical(
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; CHECK-NEXT: [[MASK:%.*]] = and i8 [[A:%.*]], 1
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; CHECK-NEXT: [[TOBOOL2:%.*]] = icmp eq i8 [[B:%.*]], 0
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; CHECK-NEXT: [[TOBOOL22:%.*]] = zext i1 [[TOBOOL2]] to i8
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; CHECK-NEXT: [[TMP1:%.*]] = xor i8 [[MASK]], 1
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; CHECK-NEXT: [[ZEXT3:%.*]] = or i8 [[TMP1]], [[TOBOOL22]]
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; CHECK-NEXT: ret i8 [[ZEXT3]]
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;
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%mask = and i8 %a, 1
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%toBool1 = icmp eq i8 %mask, 0
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%toBool2 = icmp eq i8 %b, 0
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%bothCond = select i1 %toBool1, i1 true, i1 %toBool2
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%zext = zext i1 %bothCond to i8
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ret i8 %zext
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}
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; Here, widening the or from i1 to i32 and removing one of the icmps would
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; widen an undef value (created by the out-of-range shift), increasing the
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; range of valid values for the return, so we can't do it.
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define i32 @dont_widen_undef() {
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; CHECK-LABEL: @dont_widen_undef(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[BLOCK2:%.*]]
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; CHECK: block1:
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; CHECK-NEXT: br label [[BLOCK2]]
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; CHECK: block2:
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; CHECK-NEXT: [[CMP_I:%.*]] = phi i1 [ false, [[BLOCK1:%.*]] ], [ true, [[ENTRY:%.*]] ]
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; CHECK-NEXT: [[CMP115:%.*]] = phi i1 [ true, [[BLOCK1]] ], [ false, [[ENTRY]] ]
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; CHECK-NEXT: [[CMP1:%.*]] = or i1 [[CMP_I]], [[CMP115]]
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; CHECK-NEXT: [[CONV2:%.*]] = zext i1 [[CMP1]] to i32
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; CHECK-NEXT: ret i32 [[CONV2]]
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;
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entry:
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br label %block2
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block1:
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br label %block2
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block2:
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%m.011 = phi i32 [ 33, %entry ], [ 0, %block1 ]
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%cmp.i = icmp ugt i32 %m.011, 1
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%m.1.op = lshr i32 1, %m.011
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%sext.mask = and i32 %m.1.op, 65535
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%cmp115 = icmp ne i32 %sext.mask, 0
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%cmp1 = or i1 %cmp.i, %cmp115
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%conv2 = zext i1 %cmp1 to i32
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ret i32 %conv2
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}
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define i32 @dont_widen_undef_logical() {
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; CHECK-LABEL: @dont_widen_undef_logical(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[BLOCK2:%.*]]
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; CHECK: block1:
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; CHECK-NEXT: br label [[BLOCK2]]
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; CHECK: block2:
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; CHECK-NEXT: [[CMP_I:%.*]] = phi i1 [ false, [[BLOCK1:%.*]] ], [ true, [[ENTRY:%.*]] ]
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; CHECK-NEXT: [[CMP115:%.*]] = phi i1 [ true, [[BLOCK1]] ], [ false, [[ENTRY]] ]
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; CHECK-NEXT: [[CMP1:%.*]] = or i1 [[CMP_I]], [[CMP115]]
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; CHECK-NEXT: [[CONV2:%.*]] = zext i1 [[CMP1]] to i32
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; CHECK-NEXT: ret i32 [[CONV2]]
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;
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entry:
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br label %block2
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block1:
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br label %block2
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block2:
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%m.011 = phi i32 [ 33, %entry ], [ 0, %block1 ]
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%cmp.i = icmp ugt i32 %m.011, 1
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%m.1.op = lshr i32 1, %m.011
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%sext.mask = and i32 %m.1.op, 65535
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%cmp115 = icmp ne i32 %sext.mask, 0
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%cmp1 = select i1 %cmp.i, i1 true, i1 %cmp115
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%conv2 = zext i1 %cmp1 to i32
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ret i32 %conv2
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}
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