[llvm] 6513995 - [InstSimplify] Restrict a GEP transform to avoid provenance changes

[Simonas Kazlauskas via llvm-commits]

Author: Simonas Kazlauskas
Date: 2021-03-16T18:53:05+02:00
New Revision: 6513995be37b73cb168bec5f7fa66015893659bf

URL: https://github.com/llvm/llvm-project/commit/6513995be37b73cb168bec5f7fa66015893659bf
DIFF: https://github.com/llvm/llvm-project/commit/6513995be37b73cb168bec5f7fa66015893659bf.diff

LOG: [InstSimplify] Restrict a GEP transform to avoid provenance changes

This is a follow-up to D98588, and fixes the inline `FIXME` about a GEP-related simplification not
preserving the provenance.

https://alive2.llvm.org/ce/z/qbQoAY

Additional tests were added in {rGf125f28afdb59eba29d2491dac0dfc0a7bf1b60b}

Depends on D98672

Reviewed By: lebedev.ri

Differential Revision: https://reviews.llvm.org/D98611

Added: 
    

Modified: 
    llvm/lib/Analysis/InstructionSimplify.cpp
    llvm/test/Transforms/InstSimplify/gep.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 95a4e8d82c76..7790255e22c4 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4349,11 +4349,9 @@ static Value *SimplifyGEPInst(Type *SrcTy, ArrayRef<Value *> Ops,
       // doesn't truncate the pointers.
       if (Ops[1]->getType()->getScalarSizeInBits() ==
           Q.DL.getPointerSizeInBits(AS)) {
-        auto CanSimplify = [GEPTy, &P]() -> bool {
-          // FIXME: The following transforms are only legal if P and V have the
-          // same provenance (PR44403). Check whether getUnderlyingObject() is
-          // the same?
-          return P->getType() == GEPTy;
+        auto CanSimplify = [GEPTy, &P, V = Ops[0]]() -> bool {
+          return P->getType() == GEPTy &&
+                 getUnderlyingObject(P) == getUnderlyingObject(V);
         };
         // getelementptr V, (sub P, V) -> P if P points to a type of size 1.
         if (TyAllocSize == 1 &&

diff  --git a/llvm/test/Transforms/InstSimplify/gep.ll b/llvm/test/Transforms/InstSimplify/gep.ll
index 3c460ecc4a67..e1da60ee5668 100644
--- a/llvm/test/Transforms/InstSimplify/gep.ll
+++ b/llvm/test/Transforms/InstSimplify/gep.ll
@@ -7,7 +7,12 @@ target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 
 define %struct.A* @test1(%struct.A* %b, %struct.A* %e) {
 ; CHECK-LABEL: @test1(
-; CHECK-NEXT:    ret %struct.A* [[E:%.*]]
+; CHECK-NEXT:    [[E_PTR:%.*]] = ptrtoint %struct.A* [[E:%.*]] to i64
+; CHECK-NEXT:    [[B_PTR:%.*]] = ptrtoint %struct.A* [[B:%.*]] to i64
+; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[E_PTR]], [[B_PTR]]
+; CHECK-NEXT:    [[SDIV:%.*]] = sdiv exact i64 [[SUB]], 7
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds [[STRUCT_A:%.*]], %struct.A* [[B]], i64 [[SDIV]]
+; CHECK-NEXT:    ret %struct.A* [[GEP]]
 ;
   %e_ptr = ptrtoint %struct.A* %e to i64
   %b_ptr = ptrtoint %struct.A* %b to i64
@@ -19,7 +24,11 @@ define %struct.A* @test1(%struct.A* %b, %struct.A* %e) {
 
 define i8* @test2(i8* %b, i8* %e) {
 ; CHECK-LABEL: @test2(
-; CHECK-NEXT:    ret i8* [[E:%.*]]
+; CHECK-NEXT:    [[E_PTR:%.*]] = ptrtoint i8* [[E:%.*]] to i64
+; CHECK-NEXT:    [[B_PTR:%.*]] = ptrtoint i8* [[B:%.*]] to i64
+; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[E_PTR]], [[B_PTR]]
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds i8, i8* [[B]], i64 [[SUB]]
+; CHECK-NEXT:    ret i8* [[GEP]]
 ;
   %e_ptr = ptrtoint i8* %e to i64
   %b_ptr = ptrtoint i8* %b to i64
@@ -30,7 +39,12 @@ define i8* @test2(i8* %b, i8* %e) {
 
 define i64* @test3(i64* %b, i64* %e) {
 ; CHECK-LABEL: @test3(
-; CHECK-NEXT:    ret i64* [[E:%.*]]
+; CHECK-NEXT:    [[E_PTR:%.*]] = ptrtoint i64* [[E:%.*]] to i64
+; CHECK-NEXT:    [[B_PTR:%.*]] = ptrtoint i64* [[B:%.*]] to i64
+; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[E_PTR]], [[B_PTR]]
+; CHECK-NEXT:    [[ASHR:%.*]] = ashr exact i64 [[SUB]], 3
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds i64, i64* [[B]], i64 [[ASHR]]
+; CHECK-NEXT:    ret i64* [[GEP]]
 ;
   %e_ptr = ptrtoint i64* %e to i64
   %b_ptr = ptrtoint i64* %b to i64