[llvm] cc28a75 - Let EarlyCSE fold equivalent freeze instructions
Juneyoung Lee via llvm-commits
llvm-commits at lists.llvm.org
Fri Feb 28 03:35:28 PST 2020
Author: Juneyoung Lee
Date: 2020-02-28T20:35:20+09:00
New Revision: cc28a754679a2c85625e719944154fe82491f008
URL: https://github.com/llvm/llvm-project/commit/cc28a754679a2c85625e719944154fe82491f008
DIFF: https://github.com/llvm/llvm-project/commit/cc28a754679a2c85625e719944154fe82491f008.diff
LOG: Let EarlyCSE fold equivalent freeze instructions
Summary:
This patch makes EarlyCSE fold equivalent freeze instructions.
Another optimization that I think will be useful is to remove freeze if its operand is used as a branch condition or at llvm.assume:
```
%c = ...
br i1 %c, label %A, ..
A:
%d = freeze %c ; %d can be optimized to %c because %c cannot be poison or undef (or 'br %c' would be UB otherwise)
```
If it make sense for EarlyCSE to support this as well, I will make a patch for this.
Reviewers: spatel, reames, lebedev.ri
Reviewed By: lebedev.ri
Subscribers: lebedev.ri, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D75334
Added:
Modified:
llvm/lib/Transforms/Scalar/EarlyCSE.cpp
llvm/test/Transforms/EarlyCSE/basic.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
index 588939d96a64..39c86c7fc0b6 100644
--- a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
+++ b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
@@ -114,7 +114,7 @@ struct SimpleValue {
isa<CmpInst>(Inst) || isa<SelectInst>(Inst) ||
isa<ExtractElementInst>(Inst) || isa<InsertElementInst>(Inst) ||
isa<ShuffleVectorInst>(Inst) || isa<ExtractValueInst>(Inst) ||
- isa<InsertValueInst>(Inst);
+ isa<InsertValueInst>(Inst) || isa<FreezeInst>(Inst);
}
};
@@ -268,6 +268,9 @@ static unsigned getHashValueImpl(SimpleValue Val) {
if (CastInst *CI = dyn_cast<CastInst>(Inst))
return hash_combine(CI->getOpcode(), CI->getType(), CI->getOperand(0));
+ if (FreezeInst *FI = dyn_cast<FreezeInst>(Inst))
+ return hash_combine(FI->getOpcode(), FI->getOperand(0));
+
if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(Inst))
return hash_combine(EVI->getOpcode(), EVI->getOperand(0),
hash_combine_range(EVI->idx_begin(), EVI->idx_end()));
@@ -279,7 +282,8 @@ static unsigned getHashValueImpl(SimpleValue Val) {
assert((isa<CallInst>(Inst) || isa<GetElementPtrInst>(Inst) ||
isa<ExtractElementInst>(Inst) || isa<InsertElementInst>(Inst) ||
- isa<ShuffleVectorInst>(Inst) || isa<UnaryOperator>(Inst)) &&
+ isa<ShuffleVectorInst>(Inst) || isa<UnaryOperator>(Inst) ||
+ isa<FreezeInst>(Inst)) &&
"Invalid/unknown instruction");
// Mix in the opcode.
diff --git a/llvm/test/Transforms/EarlyCSE/basic.ll b/llvm/test/Transforms/EarlyCSE/basic.ll
index 5797475c809c..25d2dc3fd9b9 100644
--- a/llvm/test/Transforms/EarlyCSE/basic.ll
+++ b/llvm/test/Transforms/EarlyCSE/basic.ll
@@ -291,3 +291,14 @@ entry:
store i32 2, i32* @c, align 4
ret void
}
+
+define i1 @cse_freeze(i1 %a) {
+entry:
+; CHECK-LABEL: @cse_freeze(
+; CHECK: %b = freeze i1 %a
+; CHECK: ret i1 %b
+ %b = freeze i1 %a
+ %c = freeze i1 %a
+ %and = and i1 %b, %c
+ ret i1 %and
+}
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