[ConstantHoisting] Avoid hoisting constants in GEPs that index into a struct type.

Summary:
Indices for GEPs that index into a struct type should always be
constants. This added more checks in `collectConstantCandidates:` which make
sure constants for GEP pointer type are not hoisted.

This fixed Bug https://bugs.llvm.org/show_bug.cgi?id=33538

Reviewers: ributzka, rnk

Reviewed By: ributzka

Subscribers: efriedma, llvm-commits, srhines, javed.absar, pirama

Differential Revision: https://reviews.llvm.org/D34576

llvm-svn: 306704

1 files changed, 37 insertions, 0 deletions

diff --git a/llvm/test/Transforms/ConstantHoisting/ARM/gep-struct-index.ll b/llvm/test/Transforms/ConstantHoisting/ARM/gep-struct-index.ll
new file mode 100644
index 00000000000..45f4500b37c
--- /dev/null
+++ b/llvm/test/Transforms/ConstantHoisting/ARM/gep-struct-index.ll
@@ -0,0 +1,37 @@
+; RUN: opt -consthoist -S < %s | FileCheck %s
+target triple = "thumbv6m-none-eabi"
+
+%T = type { i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32,
+i32, i32, i32, i32, i32, i32 }
+
+; Indices for GEPs that index into a struct type should not be hoisted.
+define i32 @test1(%T* %P) nounwind {
+; CHECK-LABEL:  @test1
+; CHECK:        %const = bitcast i32 256 to i32
+; CHECK:        %addr1 = getelementptr %T, %T* %P, i32 %const, i32 256
+; CHECK:        %addr2 = getelementptr %T, %T* %P, i32 %const, i32 256
+; The first index into the pointer is hoisted, but the second one into the
+; struct isn't.
+  %addr1 = getelementptr %T, %T* %P, i32 256, i32 256
+  %tmp1 = load i32, i32* %addr1
+  %addr2 = getelementptr %T, %T* %P, i32 256, i32 256
+  %tmp2 = load i32, i32* %addr2
+  %tmp4 = add i32 %tmp1, %tmp2
+  ret i32 %tmp4
+}
+