instcombine: alloca: Canonicalize scalar allocation array size

As a follow-up to r232200, add an `-instcombine` to canonicalize scalar
allocations to `i32 1`.  Since r232200, `iX 1` (for X != 32) are only
created by RAUWs, so this shouldn't fire too often.  Nevertheless, it's
a cheap check and a nice cleanup.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232202 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index deed58c425ee2e9758007f7f35de5af631a37481..73dd40e4d1936096b58d5f058daebc9db98a6bac 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -166,8 +166,16 @@ isOnlyCopiedFromConstantGlobal(AllocaInst *AI,
 
 static Instruction *simplifyAllocaArraySize(InstCombiner &IC, AllocaInst &AI) {
   // Check for array size of 1 (scalar allocation).
-  if (!AI.isArrayAllocation())
-    return nullptr;
+  if (!AI.isArrayAllocation()) {
+    // i32 1 is the canonical array size for scalar allocations.
+    if (AI.getArraySize()->getType()->isIntegerTy(32))
+      return nullptr;
+
+    // Canonicalize it.
+    Value *V = IC.Builder->getInt32(1);
+    AI.setOperand(0, V);
+    return &AI;
+  }
 
   // Convert: alloca Ty, C - where C is a constant != 1 into: alloca [C x Ty], 1
   if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) {

diff --git a/test/Transforms/InstCombine/alloca.ll b/test/Transforms/InstCombine/alloca.ll
index db26218f3b894a005385ec26f7ac5178f9748e77..81e2083204bad50e6cf560c7843a982b15d6bd18 100644 (file)
--- a/test/Transforms/InstCombine/alloca.ll
+++ b/test/Transforms/InstCombine/alloca.ll
@@ -155,8 +155,8 @@ define void @test10() {
 entry:
 ; ALL-LABEL: @test10(
 ; ALL: %v32 = alloca i1, align 8
-; ALL: %v64 = alloca i1, i64 1, align 8
-; ALL: %v33 = alloca i1, i33 1, align 8
+; ALL: %v64 = alloca i1, align 8
+; ALL: %v33 = alloca i1, align 8
   %v32 = alloca i1, align 8
   %v64 = alloca i1, i64 1, align 8
   %v33 = alloca i1, i33 1, align 8