[llvm] 93cbdae - [Reassociate] Avoid ConstantExpr::get()

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2022-07-04T15:17:22+02:00
New Revision: 93cbdaef0455f81ea6355f11b3d1653fae7ba05a

URL: https://github.com/llvm/llvm-project/commit/93cbdaef0455f81ea6355f11b3d1653fae7ba05a
DIFF: https://github.com/llvm/llvm-project/commit/93cbdaef0455f81ea6355f11b3d1653fae7ba05a.diff

LOG: [Reassociate] Avoid ConstantExpr::get()

Use ConstantFoldBinaryOpOperands() instead, to handle the case
where not all binary ops have a constant expression variant.

This is a bit awkward because we only want to pop the element from
Ops once we're sure that it has folded.

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/Reassociate.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index da17379793050..75f0896d48459 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -29,6 +29,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/BasicAliasAnalysis.h"
+#include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/Argument.h"
@@ -1929,11 +1930,23 @@ Value *ReassociatePass::OptimizeExpression(BinaryOperator *I,
                                            SmallVectorImpl<ValueEntry> &Ops) {
   // Now that we have the linearized expression tree, try to optimize it.
   // Start by folding any constants that we found.
+  const DataLayout &DL = I->getModule()->getDataLayout();
   Constant *Cst = nullptr;
   unsigned Opcode = I->getOpcode();
-  while (!Ops.empty() && isa<Constant>(Ops.back().Op)) {
-    Constant *C = cast<Constant>(Ops.pop_back_val().Op);
-    Cst = Cst ? ConstantExpr::get(Opcode, C, Cst) : C;
+  while (!Ops.empty()) {
+    if (auto *C = dyn_cast<Constant>(Ops.back().Op)) {
+      if (!Cst) {
+        Ops.pop_back();
+        Cst = C;
+        continue;
+      }
+      if (Constant *Res = ConstantFoldBinaryOpOperands(Opcode, C, Cst, DL)) {
+        Ops.pop_back();
+        Cst = Res;
+        continue;
+      }
+    }
+    break;
   }
   // If there was nothing but constants then we are done.
   if (Ops.empty())