[llvm] 62b74f7 - [GVN][NFC] Refactor analyzeLoadFromClobberingWrite
via llvm-commits
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Wed Mar 31 17:40:12 PDT 2021
Author: qixingxue
Date: 2021-04-01T08:35:35+08:00
New Revision: 62b74f75645f53610c1d3c5387072fc4fff98bb9
URL: https://github.com/llvm/llvm-project/commit/62b74f75645f53610c1d3c5387072fc4fff98bb9
DIFF: https://github.com/llvm/llvm-project/commit/62b74f75645f53610c1d3c5387072fc4fff98bb9.diff
LOG: [GVN][NFC] Refactor analyzeLoadFromClobberingWrite
This commit adjusts the order of two swappable if statements to
make code cleaner.
Reviewed By: lattner, nikic
Differential Revision: https://reviews.llvm.org/D99648
Added:
Modified:
llvm/lib/Transforms/Utils/VNCoercion.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/VNCoercion.cpp b/llvm/lib/Transforms/Utils/VNCoercion.cpp
index 61cd8595a73b8..6336af25ef982 100644
--- a/llvm/lib/Transforms/Utils/VNCoercion.cpp
+++ b/llvm/lib/Transforms/Utils/VNCoercion.cpp
@@ -189,14 +189,6 @@ static int analyzeLoadFromClobberingWrite(Type *LoadTy, Value *LoadPtr,
if (StoreBase != LoadBase)
return -1;
- // If the load and store are to the exact same address, they should have been
- // a must alias. AA must have gotten confused.
- // FIXME: Study to see if/when this happens. One case is forwarding a memset
- // to a load from the base of the memset.
-
- // If the load and store don't overlap at all, the store doesn't provide
- // anything to the load. In this case, they really don't alias at all, AA
- // must have gotten confused.
uint64_t LoadSize = DL.getTypeSizeInBits(LoadTy).getFixedSize();
if ((WriteSizeInBits & 7) | (LoadSize & 7))
@@ -204,15 +196,6 @@ static int analyzeLoadFromClobberingWrite(Type *LoadTy, Value *LoadPtr,
uint64_t StoreSize = WriteSizeInBits / 8; // Convert to bytes.
LoadSize /= 8;
- bool isAAFailure = false;
- if (StoreOffset < LoadOffset)
- isAAFailure = StoreOffset + int64_t(StoreSize) <= LoadOffset;
- else
- isAAFailure = LoadOffset + int64_t(LoadSize) <= StoreOffset;
-
- if (isAAFailure)
- return -1;
-
// If the Load isn't completely contained within the stored bits, we don't
// have all the bits to feed it. We could do something crazy in the future
// (issue a smaller load then merge the bits in) but this seems unlikely to be
@@ -221,6 +204,18 @@ static int analyzeLoadFromClobberingWrite(Type *LoadTy, Value *LoadPtr,
StoreOffset + StoreSize < LoadOffset + LoadSize)
return -1;
+ // If the load and store are to the exact same address, they should have been
+ // a must alias. AA must have gotten confused.
+ // FIXME: Study to see if/when this happens. One case is forwarding a memset
+ // to a load from the base of the memset.
+
+ // If the load and store don't overlap at all, the store doesn't provide
+ // anything to the load. In this case, they really don't alias at all, AA
+ // must have gotten confused. The if statement above ensure the condition
+ // that StoreOffset <= LoadOffset.
+ if (StoreOffset + int64_t(StoreSize) <= LoadOffset)
+ return -1;
+
// Okay, we can do this transformation. Return the number of bytes into the
// store that the load is.
return LoadOffset - StoreOffset;
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