Revert "Revert two GEP-related InstCombine commits"

This reverts commit r216698 which reverted r216523 and r216598.

We would attempt to perform the transformation even if the match()
failed because, as a side effect, it would set V.  This would trick us
into believing that we correctly found a place to correctly apply the
transform.

An additional test case was added to getelementptr.ll so that we might
not regress in the future.

llvm-svn: 216890

1 files changed, 73 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/getelementptr.ll b/llvm/test/Transforms/InstCombine/getelementptr.ll
index da91ada0805..b7daccc71af 100644
--- a/llvm/test/Transforms/InstCombine/getelementptr.ll
+++ b/llvm/test/Transforms/InstCombine/getelementptr.ll
@@ -6,6 +6,7 @@ target datalayout = "e-p:64:64-p1:16:16-p2:32:32:32-p3:64:64:64"
 %pair = type { i32, i32 }
 %struct.B = type { double }
 %struct.A = type { %struct.B, i32, i32 }
+%struct.C = type { [7 x i8] }
 
 
 @Global = constant [10 x i8] c"helloworld"
@@ -813,6 +814,78 @@ define i16 @test41([3 x i32] addrspace(1)* %array) {
 ; CHECK-NEXT: ret i16 8
 }
 
+define i8* @test42(i8* %c1, i8* %c2) {
+  %ptrtoint = ptrtoint i8* %c1 to i64
+  %sub = sub i64 0, %ptrtoint
+  %gep = getelementptr inbounds i8* %c2, i64 %sub
+  ret i8* %gep
+
+; CHECK-LABEL: @test42(
+; CHECK-NEXT:  [[PTRTOINT1:%.*]] = ptrtoint i8* %c1 to i64
+; CHECK-NEXT:  [[PTRTOINT2:%.*]] = ptrtoint i8* %c2 to i64
+; CHECK-NEXT:  [[SUB:%.*]] = sub i64 [[PTRTOINT2]], [[PTRTOINT1]]
+; CHECK-NEXT:  [[INTTOPTR:%.*]] = inttoptr i64 [[SUB]] to i8*
+; CHECK-NEXT:  ret i8* [[INTTOPTR]]
+}
+
+define i16* @test43(i16* %c1, i16* %c2) {
+  %ptrtoint = ptrtoint i16* %c1 to i64
+  %sub = sub i64 0, %ptrtoint
+  %shr = ashr i64 %sub, 1
+  %gep = getelementptr inbounds i16* %c2, i64 %shr
+  ret i16* %gep
+
+; CHECK-LABEL: @test43(
+; CHECK-NEXT:  [[PTRTOINT1:%.*]] = ptrtoint i16* %c1 to i64
+; CHECK-NEXT:  [[PTRTOINT2:%.*]] = ptrtoint i16* %c2 to i64
+; CHECK-NEXT:  [[SUB:%.*]] = sub i64 [[PTRTOINT2]], [[PTRTOINT1]]
+; CHECK-NEXT:  [[INTTOPTR:%.*]] = inttoptr i64 [[SUB]] to i16*
+; CHECK-NEXT:  ret i16* [[INTTOPTR]]
+}
+
+define %struct.C* @test44(%struct.C* %c1, %struct.C* %c2) {
+  %ptrtoint = ptrtoint %struct.C* %c1 to i64
+  %sub = sub i64 0, %ptrtoint
+  %shr = sdiv i64 %sub, 7
+  %gep = getelementptr inbounds %struct.C* %c2, i64 %shr
+  ret %struct.C* %gep
+
+; CHECK-LABEL: @test44(
+; CHECK-NEXT:  [[PTRTOINT1:%.*]] = ptrtoint %struct.C* %c1 to i64
+; CHECK-NEXT:  [[PTRTOINT2:%.*]] = ptrtoint %struct.C* %c2 to i64
+; CHECK-NEXT:  [[SUB:%.*]] = sub i64 [[PTRTOINT2]], [[PTRTOINT1]]
+; CHECK-NEXT:  [[INTTOPTR:%.*]] = inttoptr i64 [[SUB]] to %struct.C*
+; CHECK-NEXT:  ret %struct.C* [[INTTOPTR]]
+}
+
+define %struct.C* @test45(%struct.C* %c1, %struct.C** %c2) {
+  %ptrtoint1 = ptrtoint %struct.C* %c1 to i64
+  %ptrtoint2 = ptrtoint %struct.C** %c2 to i64
+  %sub = sub i64 %ptrtoint2, %ptrtoint1 ; C2 - C1
+  %shr = sdiv i64 %sub, 7
+  %gep = getelementptr inbounds %struct.C* %c1, i64 %shr ; C1 + (C2 - C1)
+  ret %struct.C* %gep
+
+; CHECK-LABEL: @test45(
+; CHECK-NEXT:  [[BITCAST:%.*]] = bitcast %struct.C** %c2 to %struct.C*
+; CHECK-NEXT:  ret %struct.C* [[BITCAST]]
+}
+
+define %struct.C* @test46(%struct.C* %c1, %struct.C* %c2, i64 %N) {
+  %ptrtoint = ptrtoint %struct.C* %c1 to i64
+  %sub = sub i64 0, %ptrtoint
+  %sdiv = sdiv i64 %sub, %N
+  %gep = getelementptr inbounds %struct.C* %c2, i64 %sdiv
+  ret %struct.C* %gep
+
+; CHECK-LABEL: @test46(
+; CHECK-NEXT:  [[PTRTOINT:%.*]] = ptrtoint %struct.C* %c1 to i64
+; CHECK-NEXT:  [[SUB:%.*]] = sub i64 0, [[PTRTOINT]]
+; CHECK-NEXT:  [[SDIV:%.*]] = sdiv i64 [[SUB]], %N
+; CHECK-NEXT:  [[GEP:%.*]] = getelementptr inbounds %struct.C* %c2, i64 %sdiv
+; CHECK-NEXT:  ret %struct.C* [[GEP]]
+}
+
 define i32 addrspace(1)* @ascast_0_gep(i32* %p) nounwind {
 ; CHECK-LABEL: @ascast_0_gep(
 ; CHECK-NOT: getelementptr