Merge commit 'cbe1760f0288' from llvm.org/main into next

Author: git apple-llvm automerger

llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp

@@ -2001,29 +2001,13 @@ Value *InstCombinerImpl::OptimizePointerDifference(Value *LHS, Value *RHS,
   if (!GEP1)
     return nullptr;
 
-  if (GEP2) {
-    // (gep X, ...) - (gep X, ...)
-    //
-    // Avoid duplicating the arithmetic if there are more than one non-constant
-    // indices between the two GEPs and either GEP has a non-constant index and
-    // multiple users. If zero non-constant index, the result is a constant and
-    // there is no duplication. If one non-constant index, the result is an add
-    // or sub with a constant, which is no larger than the original code, and
-    // there's no duplicated arithmetic, even if either GEP has multiple
-    // users. If more than one non-constant indices combined, as long as the GEP
-    // with at least one non-constant index doesn't have multiple users, there
-    // is no duplication.
-    unsigned NumNonConstantIndices1 = GEP1->countNonConstantIndices();
-    unsigned NumNonConstantIndices2 = GEP2->countNonConstantIndices();
-    if (NumNonConstantIndices1 + NumNonConstantIndices2 > 1 &&
-        ((NumNonConstantIndices1 > 0 && !GEP1->hasOneUse()) ||
-         (NumNonConstantIndices2 > 0 && !GEP2->hasOneUse()))) {
-      return nullptr;
-    }
-  }
+  // To avoid duplicating the offset arithmetic, rewrite the GEP to use the
+  // computed offset.
+  // TODO: We should probably do this even if there is only one GEP.
+  bool RewriteGEPs = GEP2 != nullptr;
 
   // Emit the offset of the GEP and an intptr_t.
-  Value *Result = EmitGEPOffset(GEP1);
+  Value *Result = EmitGEPOffset(GEP1, RewriteGEPs);
 
   // If this is a single inbounds GEP and the original sub was nuw,
   // then the final multiplication is also nuw.
@@ -2035,7 +2019,7 @@ Value *InstCombinerImpl::OptimizePointerDifference(Value *LHS, Value *RHS,
   // If we have a 2nd GEP of the same base pointer, subtract the offsets.
   // If both GEPs are inbounds, then the subtract does not have signed overflow.
   if (GEP2) {
-    Value *Offset = EmitGEPOffset(GEP2);
+    Value *Offset = EmitGEPOffset(GEP2, RewriteGEPs);
     Result = Builder.CreateSub(Result, Offset, "gepdiff", /* NUW */ false,
                                GEP1->isInBounds() && GEP2->isInBounds());
   }

llvm/test/Transforms/InstCombine/sub.ll

@@ -1123,7 +1123,8 @@ define i64 @test58(ptr %foo, i64 %i, i64 %j) {
 
 define i64 @test59(ptr %foo, i64 %i) {
 ; CHECK-LABEL: @test59(
-; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr inbounds [100 x [100 x i8]], ptr [[FOO:%.*]], i64 0, i64 42, i64 [[I:%.*]]
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr i8, ptr [[FOO:%.*]], i64 [[I:%.*]]
+; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr i8, ptr [[TMP1]], i64 4200
 ; CHECK-NEXT:    [[GEP2:%.*]] = getelementptr inbounds i8, ptr [[FOO]], i64 4200
 ; CHECK-NEXT:    store ptr [[GEP1]], ptr @dummy_global1, align 8
 ; CHECK-NEXT:    store ptr [[GEP2]], ptr @dummy_global2, align 8
@@ -1142,13 +1143,12 @@ define i64 @test59(ptr %foo, i64 %i) {
 
 define i64 @test60(ptr %foo, i64 %i, i64 %j) {
 ; CHECK-LABEL: @test60(
-; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr inbounds [100 x [100 x i8]], ptr [[FOO:%.*]], i64 0, i64 [[J:%.*]], i64 [[I:%.*]]
-; CHECK-NEXT:    [[GEP2:%.*]] = getelementptr inbounds i8, ptr [[FOO]], i64 4200
-; CHECK-NEXT:    [[CAST1:%.*]] = ptrtoint ptr [[GEP1]] to i64
-; CHECK-NEXT:    [[CAST2:%.*]] = ptrtoint ptr [[GEP2]] to i64
-; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[CAST1]], [[CAST2]]
+; CHECK-NEXT:    [[GEP1_IDX:%.*]] = mul nsw i64 [[J:%.*]], 100
+; CHECK-NEXT:    [[GEP1_OFFS:%.*]] = add nsw i64 [[GEP1_IDX]], [[I:%.*]]
+; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr inbounds i8, ptr [[FOO:%.*]], i64 [[GEP1_OFFS]]
+; CHECK-NEXT:    [[GEPDIFF:%.*]] = add nsw i64 [[GEP1_OFFS]], -4200
 ; CHECK-NEXT:    store ptr [[GEP1]], ptr @dummy_global1, align 8
-; CHECK-NEXT:    ret i64 [[SUB]]
+; CHECK-NEXT:    ret i64 [[GEPDIFF]]
 ;
 ; gep1 has a non-constant index and more than one uses. Shouldn't duplicate the arithmetic.
   %gep1 = getelementptr inbounds [100 x [100 x i8]], ptr %foo, i64 0, i64 %j, i64 %i
@@ -1162,13 +1162,12 @@ define i64 @test60(ptr %foo, i64 %i, i64 %j) {
 
 define i64 @test61(ptr %foo, i64 %i, i64 %j) {
 ; CHECK-LABEL: @test61(
-; CHECK-NEXT:    [[GEP1:%.*]] = getelementptr inbounds i8, ptr [[FOO:%.*]], i64 4200
-; CHECK-NEXT:    [[GEP2:%.*]] = getelementptr inbounds [100 x [100 x i8]], ptr [[FOO]], i64 0, i64 [[J:%.*]], i64 [[I:%.*]]
-; CHECK-NEXT:    [[CAST1:%.*]] = ptrtoint ptr [[GEP1]] to i64
-; CHECK-NEXT:    [[CAST2:%.*]] = ptrtoint ptr [[GEP2]] to i64
-; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[CAST1]], [[CAST2]]
+; CHECK-NEXT:    [[GEP2_IDX:%.*]] = mul nsw i64 [[J:%.*]], 100
+; CHECK-NEXT:    [[GEP2_OFFS:%.*]] = add nsw i64 [[GEP2_IDX]], [[I:%.*]]
+; CHECK-NEXT:    [[GEP2:%.*]] = getelementptr inbounds i8, ptr [[FOO:%.*]], i64 [[GEP2_OFFS]]
+; CHECK-NEXT:    [[GEPDIFF:%.*]] = sub nsw i64 4200, [[GEP2_OFFS]]
 ; CHECK-NEXT:    store ptr [[GEP2]], ptr @dummy_global2, align 8
-; CHECK-NEXT:    ret i64 [[SUB]]
+; CHECK-NEXT:    ret i64 [[GEPDIFF]]
 ;
 ; gep2 has a non-constant index and more than one uses. Shouldn't duplicate the arithmetic.
   %gep1 = getelementptr inbounds [100 x [100 x i8]], ptr %foo, i64 0, i64 42, i64 0
@@ -1186,11 +1185,8 @@ define i64 @test_sub_ptradd_multiuse(ptr %p, i64 %idx1, i64 %idx2) {
 ; CHECK-LABEL: @test_sub_ptradd_multiuse(
 ; CHECK-NEXT:    [[P1:%.*]] = getelementptr inbounds i8, ptr [[P:%.*]], i64 [[IDX1:%.*]]
 ; CHECK-NEXT:    call void @use.ptr(ptr [[P1]])
-; CHECK-NEXT:    [[P2:%.*]] = getelementptr inbounds i8, ptr [[P]], i64 [[IDX2:%.*]]
-; CHECK-NEXT:    [[P1_INT:%.*]] = ptrtoint ptr [[P1]] to i64
-; CHECK-NEXT:    [[P2_INT:%.*]] = ptrtoint ptr [[P2]] to i64
-; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[P1_INT]], [[P2_INT]]
-; CHECK-NEXT:    ret i64 [[SUB]]
+; CHECK-NEXT:    [[GEPDIFF:%.*]] = sub nsw i64 [[IDX1]], [[IDX2:%.*]]
+; CHECK-NEXT:    ret i64 [[GEPDIFF]]
 ;
   %p1 = getelementptr inbounds i8, ptr %p, i64 %idx1
   call void @use.ptr(ptr %p1)