[llvm] c165591 - [IndVars] Avoid unnecessary truncate for zext nneg use

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2023-12-22T11:30:17+01:00
New Revision: c16559137cd1ad08ef5934558829d2ff5d227d70

URL: https://github.com/llvm/llvm-project/commit/c16559137cd1ad08ef5934558829d2ff5d227d70
DIFF: https://github.com/llvm/llvm-project/commit/c16559137cd1ad08ef5934558829d2ff5d227d70.diff

LOG: [IndVars] Avoid unnecessary truncate for zext nneg use

When performing sext IV widening, if one of the narrow uses is in
a zext nneg, we can treat it like an sext and avoid the insertion
of a trunc.

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
    llvm/test/Transforms/IndVarSimplify/widen-nonnegative.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index 2f2fa3730c894a..42e7c4006b427d 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -1762,7 +1762,7 @@ Instruction *WidenIV::widenIVUse(WidenIV::NarrowIVDefUse DU, SCEVExpander &Rewri
   };
 
   // Our raison d'etre! Eliminate sign and zero extension.
-  if ((isa<SExtInst>(DU.NarrowUse) && canWidenBySExt()) ||
+  if ((match(DU.NarrowUse, m_SExtLike(m_Value())) && canWidenBySExt()) ||
       (isa<ZExtInst>(DU.NarrowUse) && canWidenByZExt())) {
     Value *NewDef = DU.WideDef;
     if (DU.NarrowUse->getType() != WideType) {

diff  --git a/llvm/test/Transforms/IndVarSimplify/widen-nonnegative.ll b/llvm/test/Transforms/IndVarSimplify/widen-nonnegative.ll
index 612e9452c6373d..739db26311f4ab 100644
--- a/llvm/test/Transforms/IndVarSimplify/widen-nonnegative.ll
+++ b/llvm/test/Transforms/IndVarSimplify/widen-nonnegative.ll
@@ -331,9 +331,7 @@ define void @zext_nneg_add_nsw(ptr %A, i32 %offset, i32 %M) {
 ; CHECK:       for.body:
 ; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[TMP1:%.*]] = add nsw i64 [[INDVARS_IV]], [[TMP0]]
-; CHECK-NEXT:    [[TMP2:%.*]] = trunc i64 [[TMP1]] to i32
-; CHECK-NEXT:    [[IDXPROM_US:%.*]] = zext nneg i32 [[TMP2]] to i64
-; CHECK-NEXT:    [[ARRAYIDX_US:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i64 [[IDXPROM_US]]
+; CHECK-NEXT:    [[ARRAYIDX_US:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i64 [[TMP1]]
 ; CHECK-NEXT:    tail call void @use_ptr(ptr [[ARRAYIDX_US]])
 ; CHECK-NEXT:    [[INDVARS_IV_NEXT]] = add nuw nsw i64 [[INDVARS_IV]], 1
 ; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp ne i64 [[INDVARS_IV_NEXT]], [[WIDE_TRIP_COUNT]]
@@ -658,9 +656,7 @@ define void @zext_nneg_mul_nsw(ptr %A, i32 %multiple, i32 %M) {
 ; CHECK:       for.body:
 ; CHECK-NEXT:    [[INDVARS_IV:%.*]] = phi i64 [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[TMP1:%.*]] = mul nsw i64 [[INDVARS_IV]], [[TMP0]]
-; CHECK-NEXT:    [[TMP2:%.*]] = trunc i64 [[TMP1]] to i32
-; CHECK-NEXT:    [[IDXPROM_US:%.*]] = zext nneg i32 [[TMP2]] to i64
-; CHECK-NEXT:    [[ARRAYIDX_US:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i64 [[IDXPROM_US]]
+; CHECK-NEXT:    [[ARRAYIDX_US:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i64 [[TMP1]]
 ; CHECK-NEXT:    tail call void @use_ptr(ptr [[ARRAYIDX_US]])
 ; CHECK-NEXT:    [[INDVARS_IV_NEXT]] = add nuw nsw i64 [[INDVARS_IV]], 1
 ; CHECK-NEXT:    [[EXITCOND:%.*]] = icmp ne i64 [[INDVARS_IV_NEXT]], [[WIDE_TRIP_COUNT]]