Remove the folding rule

  getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1) 
  to
  inttoptr (i64 0 to i8*)
from the VMCore constant folder. It didn't handle sign-extension properly
in the case where the source integer is smaller than a pointer size. And,
it relied on an assumption about sizeof(i8).

The Analysis constant folder still folds these kinds of things; it has
access to TargetData, so it can do them right.

Add a testcase which tests that the VMCore constant folder doesn't
miscompile this, and that the Analysis folder does fold it.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94750 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 84 insertions, 0 deletions

diff --git a/test/Other/constant-fold-gep.ll b/test/Other/constant-fold-gep.ll
new file mode 100644
index 0000000000..513918d58f
--- /dev/null
+++ b/test/Other/constant-fold-gep.ll
@@ -0,0 +1,84 @@
+; RUN: opt -S -o - < %s | FileCheck --check-prefix=PLAIN %s
+; RUN: opt -S -o - -instcombine -globalopt < %s | FileCheck --check-prefix=OPT %s
+
+; The automatic constant folder in opt does not have targetdata access, so
+; it can't fold gep arithmetic, in general. However, the constant folder run
+; from instcombine and global opt does, and can.
+
+; PLAIN: @G8 = global i8* getelementptr (i8* inttoptr (i32 1 to i8*), i32 -1)
+; PLAIN: @G1 = global i1* getelementptr (i1* inttoptr (i32 1 to i1*), i32 -1)
+; PLAIN: @F8 = global i8* getelementptr (i8* inttoptr (i32 1 to i8*), i32 -2)
+; PLAIN: @F1 = global i1* getelementptr (i1* inttoptr (i32 1 to i1*), i32 -2)
+; PLAIN: @H8 = global i8* getelementptr (i8* null, i32 -1)
+; PLAIN: @H1 = global i1* getelementptr (i1* null, i32 -1)
+; PLAIN: define i8* @goo8() nounwind {
+; PLAIN:   ret i8* getelementptr (i8* inttoptr (i32 1 to i8*), i32 -1)
+; PLAIN: }
+; PLAIN: define i1* @goo1() nounwind {
+; PLAIN:   ret i1* getelementptr (i1* inttoptr (i32 1 to i1*), i32 -1)
+; PLAIN: }
+; PLAIN: define i8* @foo8() nounwind {
+; PLAIN:   ret i8* getelementptr (i8* inttoptr (i32 1 to i8*), i32 -2)
+; PLAIN: }
+; PLAIN: define i1* @foo1() nounwind {
+; PLAIN:   ret i1* getelementptr (i1* inttoptr (i32 1 to i1*), i32 -2)
+; PLAIN: }
+; PLAIN: define i8* @hoo8() nounwind {
+; PLAIN:   ret i8* getelementptr (i8* null, i32 -1)
+; PLAIN: }
+; PLAIN: define i1* @hoo1() nounwind {
+; PLAIN:   ret i1* getelementptr (i1* null, i32 -1)
+; PLAIN: }
+
+; OPT: @G8 = global i8* null
+; OPT: @G1 = global i1* null
+; OPT: @F8 = global i8* inttoptr (i64 -1 to i8*)
+; OPT: @F1 = global i1* inttoptr (i64 -1 to i1*)
+; OPT: @H8 = global i8* inttoptr (i64 -1 to i8*)
+; OPT: @H1 = global i1* inttoptr (i64 -1 to i1*)
+; OPT: define i8* @goo8() nounwind {
+; OPT:   ret i8* null
+; OPT: }
+; OPT: define i1* @goo1() nounwind {
+; OPT:   ret i1* null
+; OPT: }
+; OPT: define i8* @foo8() nounwind {
+; OPT:   ret i8* inttoptr (i64 -1 to i8*)
+; OPT: }
+; OPT: define i1* @foo1() nounwind {
+; OPT:   ret i1* inttoptr (i64 -1 to i1*)
+; OPT: }
+; OPT: define i8* @hoo8() nounwind {
+; OPT:   ret i8* inttoptr (i64 -1 to i8*)
+; OPT: }
+; OPT: define i1* @hoo1() nounwind {
+; OPT:   ret i1* inttoptr (i64 -1 to i1*)
+; OPT: }
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64"
+
+@G8 = global i8* getelementptr (i8* inttoptr (i32 1 to i8*), i32 -1)
+@G1 = global i1* getelementptr (i1* inttoptr (i32 1 to i1*), i32 -1)
+@F8 = global i8* getelementptr (i8* inttoptr (i32 1 to i8*), i32 -2)
+@F1 = global i1* getelementptr (i1* inttoptr (i32 1 to i1*), i32 -2)
+@H8 = global i8* getelementptr (i8* inttoptr (i32 0 to i8*), i32 -1)
+@H1 = global i1* getelementptr (i1* inttoptr (i32 0 to i1*), i32 -1)
+
+define i8* @goo8() nounwind {
+  ret i8* getelementptr (i8* inttoptr (i32 1 to i8*), i32 -1)
+}
+define i1* @goo1() nounwind {
+  ret i1* getelementptr (i1* inttoptr (i32 1 to i1*), i32 -1)
+}
+define i8* @foo8() nounwind {
+  ret i8* getelementptr (i8* inttoptr (i32 1 to i8*), i32 -2)
+}
+define i1* @foo1() nounwind {
+  ret i1* getelementptr (i1* inttoptr (i32 1 to i1*), i32 -2)
+}
+define i8* @hoo8() nounwind {
+  ret i8* getelementptr (i8* inttoptr (i32 0 to i8*), i32 -1)
+}
+define i1* @hoo1() nounwind {
+  ret i1* getelementptr (i1* inttoptr (i32 0 to i1*), i32 -1)
+}