21e3a212c5
When we have a `phi` instruction with more than one of its incoming values being a call to `ucmp` or `scmp`, which is then compared with an integer constant, we can move the comparison through the `phi` into the incoming basic blocks because we know that a comparison of `ucmp`/`scmp` with a constant will be simplified by the next iteration of InstCombine. There's a high chance that other similar patterns can be identified, in which case they can be easily handled by the same code by moving the check for "simplifiable" instructions into a lambda.
136 lines
4.8 KiB
LLVM
136 lines
4.8 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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declare void @use(i8 %value);
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; Since we know that any comparison of ucmp/scmp with a constant will result in
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; a comparison of ucmp/scmp's operands, we can propagate such a comparison
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; through the phi node and let the next iteration of instcombine simplify it.
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define i1 @icmp_of_phi_of_scmp_with_constant(i1 %c, i16 %x, i16 %y)
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; CHECK-LABEL: define i1 @icmp_of_phi_of_scmp_with_constant(
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; CHECK-SAME: i1 [[C:%.*]], i16 [[X:%.*]], i16 [[Y:%.*]]) {
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; CHECK-NEXT: [[ENTRY:.*:]]
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; CHECK-NEXT: br i1 [[C]], label %[[TRUE:.*]], label %[[FALSE:.*]]
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; CHECK: [[TRUE]]:
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; CHECK-NEXT: [[TMP0:%.*]] = icmp slt i16 [[X]], [[Y]]
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; CHECK-NEXT: br label %[[EXIT:.*]]
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; CHECK: [[FALSE]]:
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; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i16 [[Y]], [[X]]
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; CHECK-NEXT: br label %[[EXIT]]
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; CHECK: [[EXIT]]:
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; CHECK-NEXT: [[R:%.*]] = phi i1 [ [[TMP0]], %[[TRUE]] ], [ [[TMP1]], %[[FALSE]] ]
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; CHECK-NEXT: ret i1 [[R]]
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;
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{
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entry:
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br i1 %c, label %true, label %false
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true:
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%cmp1 = call i8 @llvm.scmp(i16 %x, i16 %y)
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br label %exit
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false:
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%cmp2 = call i8 @llvm.scmp(i16 %y, i16 %x)
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br label %exit
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exit:
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%phi = phi i8 [%cmp1, %true], [%cmp2, %false]
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%r = icmp slt i8 %phi, 0
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ret i1 %r
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}
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; When one of the incoming values is ucmp/scmp and the other is not we can still perform the transformation
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define i1 @icmp_of_phi_of_one_scmp_with_constant(i1 %c, i16 %x, i16 %y, i8 %false_val)
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; CHECK-LABEL: define i1 @icmp_of_phi_of_one_scmp_with_constant(
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; CHECK-SAME: i1 [[C:%.*]], i16 [[X:%.*]], i16 [[Y:%.*]], i8 [[FALSE_VAL:%.*]]) {
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; CHECK-NEXT: [[ENTRY:.*:]]
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; CHECK-NEXT: br i1 [[C]], label %[[TRUE:.*]], label %[[FALSE:.*]]
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; CHECK: [[TRUE]]:
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; CHECK-NEXT: [[TMP0:%.*]] = icmp slt i16 [[X]], [[Y]]
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; CHECK-NEXT: br label %[[EXIT:.*]]
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; CHECK: [[FALSE]]:
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; CHECK-NEXT: [[TMP1:%.*]] = icmp slt i8 [[FALSE_VAL]], 0
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; CHECK-NEXT: br label %[[EXIT]]
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; CHECK: [[EXIT]]:
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; CHECK-NEXT: [[PHI:%.*]] = phi i1 [ [[TMP0]], %[[TRUE]] ], [ [[TMP1]], %[[FALSE]] ]
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; CHECK-NEXT: ret i1 [[PHI]]
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;
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{
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entry:
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br i1 %c, label %true, label %false
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true:
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%cmp1 = call i8 @llvm.scmp(i16 %x, i16 %y)
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br label %exit
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false:
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br label %exit
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exit:
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%phi = phi i8 [%cmp1, %true], [%false_val, %false]
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%r = icmp slt i8 %phi, 0
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ret i1 %r
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}
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; Negative test: the RHS of comparison that uses the phi node is not constant
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define i1 @icmp_of_phi_of_scmp_with_non_constant(i1 %c, i16 %x, i16 %y, i8 %cmp)
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; CHECK-LABEL: define i1 @icmp_of_phi_of_scmp_with_non_constant(
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; CHECK-SAME: i1 [[C:%.*]], i16 [[X:%.*]], i16 [[Y:%.*]], i8 [[CMP:%.*]]) {
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; CHECK-NEXT: [[ENTRY:.*:]]
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; CHECK-NEXT: br i1 [[C]], label %[[TRUE:.*]], label %[[FALSE:.*]]
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; CHECK: [[TRUE]]:
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; CHECK-NEXT: [[CMP1:%.*]] = call i8 @llvm.scmp.i8.i16(i16 [[X]], i16 [[Y]])
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; CHECK-NEXT: br label %[[EXIT:.*]]
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; CHECK: [[FALSE]]:
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; CHECK-NEXT: [[CMP2:%.*]] = call i8 @llvm.scmp.i8.i16(i16 [[Y]], i16 [[X]])
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; CHECK-NEXT: br label %[[EXIT]]
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; CHECK: [[EXIT]]:
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; CHECK-NEXT: [[PHI:%.*]] = phi i8 [ [[CMP1]], %[[TRUE]] ], [ [[CMP2]], %[[FALSE]] ]
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; CHECK-NEXT: [[R:%.*]] = icmp slt i8 [[PHI]], [[CMP]]
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; CHECK-NEXT: ret i1 [[R]]
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;
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{
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entry:
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br i1 %c, label %true, label %false
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true:
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%cmp1 = call i8 @llvm.scmp(i16 %x, i16 %y)
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br label %exit
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false:
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%cmp2 = call i8 @llvm.scmp(i16 %y, i16 %x)
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br label %exit
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exit:
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%phi = phi i8 [%cmp1, %true], [%cmp2, %false]
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%r = icmp slt i8 %phi, %cmp
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ret i1 %r
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}
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; Negative test: more than one incoming value of the phi node is not one-use
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define i1 @icmp_of_phi_of_scmp_with_constant_not_one_use(i1 %c, i16 %x, i16 %y)
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; CHECK-LABEL: define i1 @icmp_of_phi_of_scmp_with_constant_not_one_use(
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; CHECK-SAME: i1 [[C:%.*]], i16 [[X:%.*]], i16 [[Y:%.*]]) {
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; CHECK-NEXT: [[ENTRY:.*:]]
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; CHECK-NEXT: br i1 [[C]], label %[[TRUE:.*]], label %[[FALSE:.*]]
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; CHECK: [[TRUE]]:
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; CHECK-NEXT: [[CMP1:%.*]] = call i8 @llvm.scmp.i8.i16(i16 [[X]], i16 [[Y]])
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; CHECK-NEXT: call void @use(i8 [[CMP1]])
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; CHECK-NEXT: br label %[[EXIT:.*]]
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; CHECK: [[FALSE]]:
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; CHECK-NEXT: [[CMP2:%.*]] = call i8 @llvm.scmp.i8.i16(i16 [[Y]], i16 [[X]])
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; CHECK-NEXT: call void @use(i8 [[CMP2]])
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; CHECK-NEXT: br label %[[EXIT]]
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; CHECK: [[EXIT]]:
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; CHECK-NEXT: [[PHI:%.*]] = phi i8 [ [[CMP1]], %[[TRUE]] ], [ [[CMP2]], %[[FALSE]] ]
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; CHECK-NEXT: [[R:%.*]] = icmp slt i8 [[PHI]], 0
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; CHECK-NEXT: ret i1 [[R]]
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;
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{
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entry:
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br i1 %c, label %true, label %false
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true:
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%cmp1 = call i8 @llvm.scmp(i16 %x, i16 %y)
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call void @use(i8 %cmp1)
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br label %exit
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false:
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%cmp2 = call i8 @llvm.scmp(i16 %y, i16 %x)
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call void @use(i8 %cmp2)
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br label %exit
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exit:
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%phi = phi i8 [%cmp1, %true], [%cmp2, %false]
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%r = icmp slt i8 %phi, 0
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ret i1 %r
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}
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