[PATCH] D76971: Deduce attributes for aligned_alloc in InstCombine

[Uday Bondhugula via Phabricator via llvm-commits]

bondhugula updated this revision to Diff 253643.
bondhugula added a comment.

add attribute only if the alignment is a power of two


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76971/new/

https://reviews.llvm.org/D76971

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/test/Transforms/InstCombine/deref-alloc-fns.ll
  llvm/test/Transforms/InstCombine/malloc-free-delete.ll


Index: llvm/test/Transforms/InstCombine/malloc-free-delete.ll
===================================================================
--- llvm/test/Transforms/InstCombine/malloc-free-delete.ll
+++ llvm/test/Transforms/InstCombine/malloc-free-delete.ll
@@ -13,8 +13,19 @@
   ret i32 0
 }
 
+define i32 @dead_aligned_alloc(i32 %size, i32 %alignment, i8 %value) {
+; CHECK-LABEL: @dead_aligned_alloc(
+; CHECK-NEXT:    ret i32 0
+;
+  %aligned_allocation = tail call i8* @aligned_alloc(i32 %alignment, i32 %size)
+  store i8 %value, i8* %aligned_allocation
+  tail call void @free(i8* %aligned_allocation)
+  ret i32 0
+}
+
 declare noalias i8* @calloc(i32, i32) nounwind
 declare noalias i8* @malloc(i32)
+declare noalias i8* @aligned_alloc(i32, i32)
 declare void @free(i8*)
 
 define i1 @foo() {
Index: llvm/test/Transforms/InstCombine/deref-alloc-fns.ll
===================================================================
--- llvm/test/Transforms/InstCombine/deref-alloc-fns.ll
+++ llvm/test/Transforms/InstCombine/deref-alloc-fns.ll
@@ -7,6 +7,7 @@
 declare noalias nonnull i8* @_Znam(i64) ; throwing version of 'new'
 declare noalias nonnull i8* @_Znwm(i64) ; throwing version of 'new'
 declare noalias i8* @strdup(i8*)
+declare noalias i8* @aligned_alloc(i64, i64)
 
 @.str = private unnamed_addr constant [6 x i8] c"hello\00", align 1
 
@@ -28,6 +29,15 @@
   ret i8* %call
 }
 
+define noalias i8* @aligned_alloc_constant_size() {
+; CHECK-LABEL: @aligned_alloc_constant_size(
+; CHECK-NEXT:    [[CALL:%.*]] = tail call noalias align 32 dereferenceable_or_null(512) i8* @aligned_alloc(i64 32, i64 512)
+; CHECK-NEXT:    ret i8* [[CALL]]
+;
+  %call = tail call noalias i8* @aligned_alloc(i64 32, i64 512)
+  ret i8* %call
+}
+
 define noalias i8* @malloc_constant_size2() {
 ; CHECK-LABEL: @malloc_constant_size2(
 ; CHECK-NEXT:    [[CALL:%.*]] = tail call noalias dereferenceable_or_null(80) i8* @malloc(i64 40)
@@ -46,7 +56,6 @@
   ret i8* %call
 }
 
-
 define noalias i8* @malloc_constant_zero_size() {
 ; CHECK-LABEL: @malloc_constant_zero_size(
 ; CHECK-NEXT:    [[CALL:%.*]] = tail call noalias i8* @malloc(i64 0)
Index: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -4179,7 +4179,7 @@
       return replaceOperand(*II, 2,
           ConstantInt::get(OpIntTy, GCR.getBasePtrIndex()));
     }
-    
+
     // Translate facts known about a pointer before relocating into
     // facts about the relocate value, while being careful to
     // preserve relocation semantics.
@@ -4425,6 +4425,15 @@
       Call.addAttribute(AttributeList::ReturnIndex,
                         Attribute::getWithDereferenceableOrNullBytes(
                             Call.getContext(), Op0C->getZExtValue()));
+  } else if (isAlignedAllocLikeFn(&Call, TLI) && Op1C) {
+    Call.addAttribute(AttributeList::ReturnIndex,
+                      Attribute::getWithDereferenceableOrNullBytes(
+                          Call.getContext(), Op1C->getZExtValue()));
+    uint64_t AlignmentVal = Op0C->getZExtValue();
+    if (llvm::isPowerOf2_64(AlignmentVal))
+      Call.addAttribute(
+          AttributeList::ReturnIndex,
+          Attribute::getWithAlignment(Call.getContext(), Align(AlignmentVal)));
   } else if (isReallocLikeFn(&Call, TLI) && Op1C) {
     Call.addAttribute(AttributeList::ReturnIndex,
                       Attribute::getWithDereferenceableOrNullBytes(


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