diff options
| author | Sanjay Patel <spatel@rotateright.com> | 2020-01-09 09:02:53 -0500 |
|---|---|---|
| committer | Sanjay Patel <spatel@rotateright.com> | 2020-01-09 09:04:20 -0500 |
| commit | f53b38d12a7b9c6754d5bc91483efab935b5c012 (patch) | |
| tree | 6775a0911a6c91c3c41785c5161eebe77adab89e | |
| parent | 173b711e83d7b61a46f55eb44f03ea98f69a1dd6 (diff) | |
| download | bcm5719-llvm-f53b38d12a7b9c6754d5bc91483efab935b5c012.tar.gz bcm5719-llvm-f53b38d12a7b9c6754d5bc91483efab935b5c012.zip | |
[InstSimplify] select Cond, true, false --> Cond
This is step 1 of damage control assuming that we need to remove several
over-reaching folds for select-of-booleans because they can cause
miscompiles as shown in D72396.
The scalar case seems obviously safe:
https://rise4fun.com/Alive/jSj
And I don't think there's any danger for vectors either - if the
condition is poisoned, then the select must be poisoned too, so undef
elements don't make any difference.
Differential Revision: https://reviews.llvm.org/D72412
| -rw-r--r-- | llvm/lib/Analysis/InstructionSimplify.cpp | 9 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstSimplify/select.ll | 9 |
2 files changed, 12 insertions, 6 deletions
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp index afcca2ab1fa..d7510c89910 100644 --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -3996,6 +3996,15 @@ static Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal, return FalseVal; } + // select i1 Cond, i1 true, i1 false --> i1 Cond + assert(Cond->getType()->isIntOrIntVectorTy(1) && + "Select must have bool or bool vector condition"); + assert(TrueVal->getType() == FalseVal->getType() && + "Select must have same types for true/false ops"); + if (Cond->getType() == TrueVal->getType() && + match(TrueVal, m_One()) && match(FalseVal, m_ZeroInt())) + return Cond; + // select ?, X, X -> X if (TrueVal == FalseVal) return TrueVal; diff --git a/llvm/test/Transforms/InstSimplify/select.ll b/llvm/test/Transforms/InstSimplify/select.ll index 5581a3bd747..4fe499ad4a2 100644 --- a/llvm/test/Transforms/InstSimplify/select.ll +++ b/llvm/test/Transforms/InstSimplify/select.ll @@ -3,8 +3,7 @@ define i1 @bool_true_or_false(i1 %cond) { ; CHECK-LABEL: @bool_true_or_false( -; CHECK-NEXT: [[S:%.*]] = select i1 [[COND:%.*]], i1 true, i1 false -; CHECK-NEXT: ret i1 [[S]] +; CHECK-NEXT: ret i1 [[COND:%.*]] ; %s = select i1 %cond, i1 true, i1 false ret i1 %s @@ -12,8 +11,7 @@ define i1 @bool_true_or_false(i1 %cond) { define <2 x i1> @bool_true_or_false_vec(<2 x i1> %cond) { ; CHECK-LABEL: @bool_true_or_false_vec( -; CHECK-NEXT: [[S:%.*]] = select <2 x i1> [[COND:%.*]], <2 x i1> <i1 true, i1 true>, <2 x i1> zeroinitializer -; CHECK-NEXT: ret <2 x i1> [[S]] +; CHECK-NEXT: ret <2 x i1> [[COND:%.*]] ; %s = select <2 x i1> %cond, <2 x i1> <i1 true, i1 true>, <2 x i1> zeroinitializer ret <2 x i1> %s @@ -21,8 +19,7 @@ define <2 x i1> @bool_true_or_false_vec(<2 x i1> %cond) { define <2 x i1> @bool_true_or_false_vec_undef(<2 x i1> %cond) { ; CHECK-LABEL: @bool_true_or_false_vec_undef( -; CHECK-NEXT: [[S:%.*]] = select <2 x i1> [[COND:%.*]], <2 x i1> <i1 undef, i1 true>, <2 x i1> <i1 false, i1 undef> -; CHECK-NEXT: ret <2 x i1> [[S]] +; CHECK-NEXT: ret <2 x i1> [[COND:%.*]] ; %s = select <2 x i1> %cond, <2 x i1> <i1 undef, i1 true>, <2 x i1> <i1 false, i1 undef> ret <2 x i1> %s |
