[llvm] 0104f37 - [InstCombine] Use a cl::opt to control calls to getOrEnforceKnownAlignment in LoadInst and StoreInst

[Dhruv Chawla via llvm-commits]

Author: Dhruv Chawla
Date: 2023-09-20T12:08:14+05:30
New Revision: 0104f37f1626057a856b57f8acdd2b7407a8b01f

URL: https://github.com/llvm/llvm-project/commit/0104f37f1626057a856b57f8acdd2b7407a8b01f
DIFF: https://github.com/llvm/llvm-project/commit/0104f37f1626057a856b57f8acdd2b7407a8b01f.diff

LOG: [InstCombine] Use a cl::opt to control calls to getOrEnforceKnownAlignment in LoadInst and StoreInst

This is in preparation for the InferAlignment pass which handles
inferring alignment for instructions separately. It is better to handle
this as a separate pass as inferring alignment is quite costly, and
InstCombine running multiple times in the pass pipeline makes it even
more so.

Differential Revision: https://reviews.llvm.org/D158527

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index e176d1bea25a0ed..3767ecd6539f3b9 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -36,6 +36,8 @@ static cl::opt<unsigned> MaxCopiedFromConstantUsers(
     cl::desc("Maximum users to visit in copy from constant transform"),
     cl::Hidden);
 
+extern cl::opt<bool> EnableInferAlignmentPass;
+
 /// isOnlyCopiedFromConstantMemory - Recursively walk the uses of a (derived)
 /// pointer to an alloca.  Ignore any reads of the pointer, return false if we
 /// see any stores or other unknown uses.  If we see pointer arithmetic, keep
@@ -1048,11 +1050,13 @@ Instruction *InstCombinerImpl::visitLoadInst(LoadInst &LI) {
   if (Instruction *Res = combineLoadToOperationType(*this, LI))
     return Res;
 
-  // Attempt to improve the alignment.
-  Align KnownAlign = getOrEnforceKnownAlignment(
-      Op, DL.getPrefTypeAlign(LI.getType()), DL, &LI, &AC, &DT);
-  if (KnownAlign > LI.getAlign())
-    LI.setAlignment(KnownAlign);
+  if (!EnableInferAlignmentPass) {
+    // Attempt to improve the alignment.
+    Align KnownAlign = getOrEnforceKnownAlignment(
+        Op, DL.getPrefTypeAlign(LI.getType()), DL, &LI, &AC, &DT);
+    if (KnownAlign > LI.getAlign())
+      LI.setAlignment(KnownAlign);
+  }
 
   // Replace GEP indices if possible.
   if (Instruction *NewGEPI = replaceGEPIdxWithZero(*this, Op, LI))
@@ -1445,11 +1449,13 @@ Instruction *InstCombinerImpl::visitStoreInst(StoreInst &SI) {
   if (combineStoreToValueType(*this, SI))
     return eraseInstFromFunction(SI);
 
-  // Attempt to improve the alignment.
-  const Align KnownAlign = getOrEnforceKnownAlignment(
-      Ptr, DL.getPrefTypeAlign(Val->getType()), DL, &SI, &AC, &DT);
-  if (KnownAlign > SI.getAlign())
-    SI.setAlignment(KnownAlign);
+  if (!EnableInferAlignmentPass) {
+    // Attempt to improve the alignment.
+    const Align KnownAlign = getOrEnforceKnownAlignment(
+        Ptr, DL.getPrefTypeAlign(Val->getType()), DL, &SI, &AC, &DT);
+    if (KnownAlign > SI.getAlign())
+      SI.setAlignment(KnownAlign);
+  }
 
   // Try to canonicalize the stored type.
   if (unpackStoreToAggregate(*this, SI))