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[SCCP] Infer nuw for gep nusw with non-negative offsets #118819

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Merged
merged 1 commit into from
Dec 6, 2024
Merged

[SCCP] Infer nuw for gep nusw with non-negative offsets #118819

merged 1 commit into from
Dec 6, 2024

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@nikic nikic commented Dec 5, 2024

If the GEP is nusw/inbounds and has all-non-negative offsets infer nuw as well.

This doesn't have measurable compile-time impact.

Proof: https://alive2.llvm.org/ce/z/ihztLy

@nikic nikic requested review from fhahn and dtcxzyw December 5, 2024 15:14
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llvmbot commented Dec 5, 2024 •
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@llvm/pr-subscribers-clang
@llvm/pr-subscribers-llvm-analysis
@llvm/pr-subscribers-llvm-transforms

@llvm/pr-subscribers-function-specialization

Author: Nikita Popov (nikic)

Changes

If the GEP is nusw/inbounds and has all-non-negative offsets infer nuw as well.

This doesn't have measurable compile-time impact.

Proof: https://alive2.llvm.org/ce/z/ihztLy

Full diff: https://github.com/llvm/llvm-project/pull/118819.diff

5 Files Affected:

  • (modified) llvm/lib/Transforms/Utils/SCCPSolver.cpp (+10)
  • (modified) llvm/test/Transforms/SCCP/conditions-iter-order.ll (+3-3)
  • (modified) llvm/test/Transforms/SCCP/gep-nuw.ll (+2-2)
  • (modified) llvm/test/Transforms/SCCP/ipsccp-ssa-copy-nested-conds.ll (+2-2)
  • (modified) llvm/test/Transforms/SCCP/widening.ll (+8-8)
diff --git a/llvm/lib/Transforms/Utils/SCCPSolver.cpp b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
index 4225e7e80fda6f..81aa7ce1cfe660 100644
--- a/llvm/lib/Transforms/Utils/SCCPSolver.cpp
+++ b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
@@ -147,6 +147,16 @@ static bool refineInstruction(SCCPSolver &Solver,
         Changed = true;
       }
     }
+  } else if (auto *GEP = dyn_cast<GetElementPtrInst>(&Inst)) {
+    if (GEP->hasNoUnsignedWrap() || !GEP->hasNoUnsignedSignedWrap())
+      return false;
+
+    if (all_of(GEP->indices(),
+               [&](Value *V) { return GetRange(V).isAllNonNegative(); })) {
+      GEP->setNoWrapFlags(GEP->getNoWrapFlags() |
+                          GEPNoWrapFlags::noUnsignedWrap());
+      Changed = true;
+    }
   }
 
   return Changed;
diff --git a/llvm/test/Transforms/SCCP/conditions-iter-order.ll b/llvm/test/Transforms/SCCP/conditions-iter-order.ll
index c7f977b8ab83ae..1e8ba6197ad5f4 100644
--- a/llvm/test/Transforms/SCCP/conditions-iter-order.ll
+++ b/llvm/test/Transforms/SCCP/conditions-iter-order.ll
@@ -13,17 +13,17 @@ define internal ptr @spam(ptr %arg) {
 ; CHECK-NEXT:    [[TMP:%.*]] = call ptr @malloc(i64 10368)
 ; CHECK-NEXT:    [[TMP5:%.*]] = load i32, ptr [[ARG:%.*]], align 8
 ; CHECK-NEXT:    [[TMP6:%.*]] = add i32 [[TMP5]], 1
-; CHECK-NEXT:    [[TMP7:%.*]] = getelementptr inbounds i32, ptr [[ARG]], i32 1
+; CHECK-NEXT:    [[TMP7:%.*]] = getelementptr inbounds nuw i32, ptr [[ARG]], i32 1
 ; CHECK-NEXT:    [[TMP10:%.*]] = icmp ne ptr [[TMP7]], null
 ; CHECK-NEXT:    br i1 [[TMP10]], label [[BB17:%.*]], label [[BB13:%.*]]
 ; CHECK:       bb13:
-; CHECK-NEXT:    [[TMP14:%.*]] = getelementptr inbounds i32, ptr [[ARG]], i32 2
+; CHECK-NEXT:    [[TMP14:%.*]] = getelementptr inbounds nuw i32, ptr [[ARG]], i32 2
 ; CHECK-NEXT:    [[TMP15:%.*]] = load i32, ptr [[TMP14]], align 8
 ; CHECK-NEXT:    [[TMP16:%.*]] = add i32 [[TMP15]], 1
 ; CHECK-NEXT:    br label [[BB30:%.*]]
 ; CHECK:       bb17:
 ; CHECK-NEXT:    [[TMP18:%.*]] = icmp eq i32 [[TMP6]], [[TMP5]]
-; CHECK-NEXT:    [[TMP19:%.*]] = getelementptr inbounds i32, ptr [[ARG]], i32 3
+; CHECK-NEXT:    [[TMP19:%.*]] = getelementptr inbounds nuw i32, ptr [[ARG]], i32 3
 ; CHECK-NEXT:    [[TMP20:%.*]] = load i32, ptr [[TMP19]], align 8
 ; CHECK-NEXT:    br i1 [[TMP18]], label [[BB30]], label [[BB13]]
 ; CHECK:       bb30:
diff --git a/llvm/test/Transforms/SCCP/gep-nuw.ll b/llvm/test/Transforms/SCCP/gep-nuw.ll
index 298c14adc92a45..4d25642eb85750 100644
--- a/llvm/test/Transforms/SCCP/gep-nuw.ll
+++ b/llvm/test/Transforms/SCCP/gep-nuw.ll
@@ -6,7 +6,7 @@ define ptr @gep_nusw_nneg(ptr %p, i32 %x, i32 %y) {
 ; CHECK-SAME: ptr [[P:%.*]], i32 [[X:%.*]], i32 [[Y:%.*]]) {
 ; CHECK-NEXT:    [[X_EXT:%.*]] = zext i32 [[X]] to i64
 ; CHECK-NEXT:    [[Y_EXT:%.*]] = zext i32 [[Y]] to i64
-; CHECK-NEXT:    [[GEP:%.*]] = getelementptr nusw [1 x i8], ptr [[P]], i64 [[X_EXT]], i64 [[Y_EXT]]
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr nusw nuw [1 x i8], ptr [[P]], i64 [[X_EXT]], i64 [[Y_EXT]]
 ; CHECK-NEXT:    ret ptr [[GEP]]
 ;
   %x.ext = zext i32 %x to i64
@@ -20,7 +20,7 @@ define ptr @gep_inbounds_nneg(ptr %p, i32 %x, i32 %y) {
 ; CHECK-SAME: ptr [[P:%.*]], i32 [[X:%.*]], i32 [[Y:%.*]]) {
 ; CHECK-NEXT:    [[X_EXT:%.*]] = zext i32 [[X]] to i64
 ; CHECK-NEXT:    [[Y_EXT:%.*]] = zext i32 [[Y]] to i64
-; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds [1 x i8], ptr [[P]], i64 [[X_EXT]], i64 [[Y_EXT]]
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds nuw [1 x i8], ptr [[P]], i64 [[X_EXT]], i64 [[Y_EXT]]
 ; CHECK-NEXT:    ret ptr [[GEP]]
 ;
   %x.ext = zext i32 %x to i64
diff --git a/llvm/test/Transforms/SCCP/ipsccp-ssa-copy-nested-conds.ll b/llvm/test/Transforms/SCCP/ipsccp-ssa-copy-nested-conds.ll
index 55a7fdf7197e5a..752e5038033106 100644
--- a/llvm/test/Transforms/SCCP/ipsccp-ssa-copy-nested-conds.ll
+++ b/llvm/test/Transforms/SCCP/ipsccp-ssa-copy-nested-conds.ll
@@ -15,11 +15,11 @@ define i32 @check(ptr %node) {
 ; CHECK:       if.end:
 ; CHECK-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[NODE]], align 8
 ; CHECK-NEXT:    [[CALL:%.*]] = call i32 @check(ptr [[TMP0]])
-; CHECK-NEXT:    [[RIGHT:%.*]] = getelementptr inbounds [[STRUCT_NODE:%.*]], ptr [[NODE]], i32 0, i32 1
+; CHECK-NEXT:    [[RIGHT:%.*]] = getelementptr inbounds nuw [[STRUCT_NODE:%.*]], ptr [[NODE]], i32 0, i32 1
 ; CHECK-NEXT:    [[TMP1:%.*]] = load ptr, ptr [[RIGHT]], align 8
 ; CHECK-NEXT:    [[CALL1:%.*]] = call i32 @check(ptr [[TMP1]])
 ; CHECK-NEXT:    [[TMP2:%.*]] = load ptr, ptr [[RIGHT]], align 8
-; CHECK-NEXT:    [[HEIGHT:%.*]] = getelementptr inbounds [[STRUCT_NODE]], ptr [[TMP2]], i32 0, i32 2
+; CHECK-NEXT:    [[HEIGHT:%.*]] = getelementptr inbounds nuw [[STRUCT_NODE]], ptr [[TMP2]], i32 0, i32 2
 ; CHECK-NEXT:    [[TMP3:%.*]] = load i32, ptr [[HEIGHT]], align 4
 ; CHECK-NEXT:    [[CMP3:%.*]] = icmp ne i32 [[TMP3]], [[CALL1]]
 ; CHECK-NEXT:    br i1 [[CMP3]], label [[IF_THEN4:%.*]], label [[IF_END5:%.*]]
diff --git a/llvm/test/Transforms/SCCP/widening.ll b/llvm/test/Transforms/SCCP/widening.ll
index 144c3fd54e75b6..8c661bee8f5990 100644
--- a/llvm/test/Transforms/SCCP/widening.ll
+++ b/llvm/test/Transforms/SCCP/widening.ll
@@ -566,7 +566,7 @@ declare void @llvm.memcpy.p0.p0.i64(ptr noalias nocapture writeonly, ptr noalias
 define linkonce_odr dereferenceable(1) ptr @spam(ptr %arg, i32 %arg1) align 2 {
 ; SCCP-LABEL: @spam(
 ; SCCP-NEXT:  bb:
-; SCCP-NEXT:    [[TMP:%.*]] = getelementptr inbounds [[STRUCT_BAZ_1:%.*]], ptr [[ARG:%.*]], i32 0, i32 3
+; SCCP-NEXT:    [[TMP:%.*]] = getelementptr inbounds nuw [[STRUCT_BAZ_1:%.*]], ptr [[ARG:%.*]], i32 0, i32 3
 ; SCCP-NEXT:    [[TMP2:%.*]] = load ptr, ptr [[TMP]], align 8
 ; SCCP-NEXT:    [[TMP3:%.*]] = sext i32 [[ARG1:%.*]] to i64
 ; SCCP-NEXT:    [[TMP4:%.*]] = getelementptr inbounds i8, ptr [[TMP2]], i64 [[TMP3]]
@@ -574,7 +574,7 @@ define linkonce_odr dereferenceable(1) ptr @spam(ptr %arg, i32 %arg1) align 2 {
 ;
 ; IPSCCP-LABEL: @spam(
 ; IPSCCP-NEXT:  bb:
-; IPSCCP-NEXT:    [[TMP:%.*]] = getelementptr inbounds [[STRUCT_BAZ_1:%.*]], ptr [[ARG:%.*]], i32 0, i32 3
+; IPSCCP-NEXT:    [[TMP:%.*]] = getelementptr inbounds nuw [[STRUCT_BAZ_1:%.*]], ptr [[ARG:%.*]], i32 0, i32 3
 ; IPSCCP-NEXT:    [[TMP2:%.*]] = load ptr, ptr [[TMP]], align 8
 ; IPSCCP-NEXT:    [[TMP3:%.*]] = sext i32 [[ARG1:%.*]] to i64
 ; IPSCCP-NEXT:    [[TMP4:%.*]] = getelementptr inbounds i8, ptr [[TMP2]], i64 [[TMP3]]
@@ -595,7 +595,7 @@ define ptr @wobble(ptr %arg, i32 %arg1) align 2 {
 ; SCCP-NEXT:    [[TMP2:%.*]] = xor i32 [[TMP]], [[ARG1]]
 ; SCCP-NEXT:    [[TMP3:%.*]] = and i32 [[TMP2]], 65535
 ; SCCP-NEXT:    [[TMP4:%.*]] = mul i32 [[ARG1]], 8
-; SCCP-NEXT:    [[TMP5:%.*]] = getelementptr inbounds [[STRUCT_BLAM_2:%.*]], ptr [[ARG:%.*]], i32 0, i32 1
+; SCCP-NEXT:    [[TMP5:%.*]] = getelementptr inbounds nuw [[STRUCT_BLAM_2:%.*]], ptr [[ARG:%.*]], i32 0, i32 1
 ; SCCP-NEXT:    [[TMP6:%.*]] = load i32, ptr [[TMP5]], align 8
 ; SCCP-NEXT:    [[TMP7:%.*]] = and i32 [[TMP4]], [[TMP6]]
 ; SCCP-NEXT:    br label [[BB8:%.*]]
@@ -609,7 +609,7 @@ define ptr @wobble(ptr %arg, i32 %arg1) align 2 {
 ; SCCP-NEXT:    [[TMP15:%.*]] = add i32 [[TMP7]], [[TMP11]]
 ; SCCP-NEXT:    [[TMP16:%.*]] = mul i32 [[TMP15]], 4
 ; SCCP-NEXT:    [[TMP17]] = call dereferenceable(1) ptr @spam(ptr [[ARG]], i32 [[TMP16]])
-; SCCP-NEXT:    [[TMP19:%.*]] = getelementptr inbounds i8, ptr [[TMP17]], i64 2
+; SCCP-NEXT:    [[TMP19:%.*]] = getelementptr inbounds nuw i8, ptr [[TMP17]], i64 2
 ; SCCP-NEXT:    [[TMP20:%.*]] = load i8, ptr [[TMP19]], align 1
 ; SCCP-NEXT:    [[TMP21:%.*]] = zext i8 [[TMP20]] to i32
 ; SCCP-NEXT:    [[TMP22:%.*]] = icmp eq i32 [[TMP21]], 0
@@ -632,7 +632,7 @@ define ptr @wobble(ptr %arg, i32 %arg1) align 2 {
 ; SCCP-NEXT:    [[TMP34:%.*]] = icmp eq i32 [[TMP11]], 0
 ; SCCP-NEXT:    br i1 [[TMP34]], label [[BB35:%.*]], label [[BB37:%.*]]
 ; SCCP:       bb35:
-; SCCP-NEXT:    [[TMP36:%.*]] = getelementptr inbounds i8, ptr [[TMP32]], i64 1
+; SCCP-NEXT:    [[TMP36:%.*]] = getelementptr inbounds nuw i8, ptr [[TMP32]], i64 1
 ; SCCP-NEXT:    br label [[BB66:%.*]]
 ; SCCP:       bb37:
 ; SCCP-NEXT:    [[C_2:%.*]] = icmp eq i32 [[TMP11]], 8
@@ -677,7 +677,7 @@ define ptr @wobble(ptr %arg, i32 %arg1) align 2 {
 ; IPSCCP-NEXT:    [[TMP2:%.*]] = xor i32 [[TMP]], [[ARG1]]
 ; IPSCCP-NEXT:    [[TMP3:%.*]] = and i32 [[TMP2]], 65535
 ; IPSCCP-NEXT:    [[TMP4:%.*]] = mul i32 [[ARG1]], 8
-; IPSCCP-NEXT:    [[TMP5:%.*]] = getelementptr inbounds [[STRUCT_BLAM_2:%.*]], ptr [[ARG:%.*]], i32 0, i32 1
+; IPSCCP-NEXT:    [[TMP5:%.*]] = getelementptr inbounds nuw [[STRUCT_BLAM_2:%.*]], ptr [[ARG:%.*]], i32 0, i32 1
 ; IPSCCP-NEXT:    [[TMP6:%.*]] = load i32, ptr [[TMP5]], align 8
 ; IPSCCP-NEXT:    [[TMP7:%.*]] = and i32 [[TMP4]], [[TMP6]]
 ; IPSCCP-NEXT:    br label [[BB8:%.*]]
@@ -691,7 +691,7 @@ define ptr @wobble(ptr %arg, i32 %arg1) align 2 {
 ; IPSCCP-NEXT:    [[TMP15:%.*]] = add i32 [[TMP7]], [[TMP11]]
 ; IPSCCP-NEXT:    [[TMP16:%.*]] = mul i32 [[TMP15]], 4
 ; IPSCCP-NEXT:    [[TMP17]] = call dereferenceable(1) ptr @spam(ptr [[ARG]], i32 [[TMP16]])
-; IPSCCP-NEXT:    [[TMP19:%.*]] = getelementptr inbounds i8, ptr [[TMP17]], i64 2
+; IPSCCP-NEXT:    [[TMP19:%.*]] = getelementptr inbounds nuw i8, ptr [[TMP17]], i64 2
 ; IPSCCP-NEXT:    [[TMP20:%.*]] = load i8, ptr [[TMP19]], align 1
 ; IPSCCP-NEXT:    [[TMP21:%.*]] = zext i8 [[TMP20]] to i32
 ; IPSCCP-NEXT:    [[TMP22:%.*]] = icmp eq i32 [[TMP21]], 0
@@ -714,7 +714,7 @@ define ptr @wobble(ptr %arg, i32 %arg1) align 2 {
 ; IPSCCP-NEXT:    [[TMP34:%.*]] = icmp eq i32 [[TMP11]], 0
 ; IPSCCP-NEXT:    br i1 [[TMP34]], label [[BB35:%.*]], label [[BB37:%.*]]
 ; IPSCCP:       bb35:
-; IPSCCP-NEXT:    [[TMP36:%.*]] = getelementptr inbounds i8, ptr [[TMP32]], i64 1
+; IPSCCP-NEXT:    [[TMP36:%.*]] = getelementptr inbounds nuw i8, ptr [[TMP32]], i64 1
 ; IPSCCP-NEXT:    br label [[BB66:%.*]]
 ; IPSCCP:       bb37:
 ; IPSCCP-NEXT:    [[C_2:%.*]] = icmp eq i32 [[TMP11]], 8

@nikic
[SCCP] Infer nuw for gep nusw with non-negative offsets
1dadf4d 
If the GEP is nusw/inbounds and has all-non-negative offsets
infer nuw as well.

Proof: https://alive2.llvm.org/ce/z/ihztLy
@llvmbot llvmbot added clang Clang issues not falling into any other category llvm:analysis Includes value tracking, cost tables and constant folding labels Dec 5, 2024
This was referenced Dec 6, 2024
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dtcxzyw
dtcxzyw approved these changes Dec 6, 2024
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LGTM.

@nikic nikic merged commit b569ec6 into llvm:main Dec 6, 2024
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@nikic nikic deleted the sccp-gep-nuw branch December 6, 2024 08:52
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@dtcxzyw dtcxzyw dtcxzyw approved these changes

@fhahn fhahn Awaiting requested review from fhahn

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