[SimplifyLibCalls] Don't confuse strcpy_chk for stpcpy_chk.

This was introduced in a faulty refactoring (r225640, mea culpa):
the tests weren't testing the return values, so, for both
__strcpy_chk and __stpcpy_chk, we would return the end of the
buffer (matching stpcpy) instead of the beginning (for strcpy).

The root cause was the prefix "__" being ignored when comparing,
which made us always pick LibFunc::stpcpy_chk.
Pass the LibFunc::Func directly to avoid this kind of error.
Also, make the testcases as explicit as possible to prevent this.

The now-useful testcases expose another, entangled, stpcpy problem,
with the further simplification.  This was introduced in a
refactoring (r225640) to match the original behavior.

However, this leads to problems when successive simplifications
generate several similar instructions, none of which are removed
by the custom replaceAllUsesWith.

For instance, InstCombine (the main user) doesn't erase the
instruction in its custom RAUW.  When trying to simplify say
__stpcpy_chk:
- first, an stpcpy is created (fortified simplifier),
- second, a memcpy is created (normal simplifier), but the
  stpcpy call isn't removed.
- third, InstCombine later revisits the instructions,
  and simplifies the first stpcpy to a memcpy.  We now have
  two memcpys.

llvm-svn: 227250

1 files changed, 20 insertions, 16 deletions

diff --git a/llvm/test/Transforms/InstCombine/memmove_chk-1.ll b/llvm/test/Transforms/InstCombine/memmove_chk-1.ll
index 6d93bbbf959..e4e1f6eedf3 100644
--- a/llvm/test/Transforms/InstCombine/memmove_chk-1.ll
+++ b/llvm/test/Transforms/InstCombine/memmove_chk-1.ll
@@ -15,46 +15,50 @@ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f3
 
 ; Check cases where dstlen >= len.
 
-define void @test_simplify1() {
+define i8* @test_simplify1() {
 ; CHECK-LABEL: @test_simplify1(
   %dst = bitcast %struct.T1* @t1 to i8*
   %src = bitcast %struct.T2* @t2 to i8*
 
-; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64
-  call i8* @__memmove_chk(i8* %dst, i8* %src, i64 1824, i64 1824)
-  ret void
+; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* bitcast (%struct.T1* @t1 to i8*), i8* bitcast (%struct.T2* @t2 to i8*), i64 1824, i32 4, i1 false)
+; CHECK-NEXT: ret i8* bitcast (%struct.T1* @t1 to i8*)
+  %ret = call i8* @__memmove_chk(i8* %dst, i8* %src, i64 1824, i64 1824)
+  ret i8* %ret
 }
 
-define void @test_simplify2() {
+define i8* @test_simplify2() {
 ; CHECK-LABEL: @test_simplify2(
   %dst = bitcast %struct.T1* @t1 to i8*
   %src = bitcast %struct.T3* @t3 to i8*
 
-; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64
-  call i8* @__memmove_chk(i8* %dst, i8* %src, i64 1824, i64 2848)
-  ret void
+; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* bitcast (%struct.T1* @t1 to i8*), i8* bitcast (%struct.T3* @t3 to i8*), i64 1824, i32 4, i1 false)
+; CHECK-NEXT: ret i8* bitcast (%struct.T1* @t1 to i8*)
+  %ret = call i8* @__memmove_chk(i8* %dst, i8* %src, i64 1824, i64 2848)
+  ret i8* %ret
 }
 
 ; Check cases where dstlen < len.
 
-define void @test_no_simplify1() {
+define i8* @test_no_simplify1() {
 ; CHECK-LABEL: @test_no_simplify1(
   %dst = bitcast %struct.T3* @t3 to i8*
   %src = bitcast %struct.T1* @t1 to i8*
 
-; CHECK-NEXT: call i8* @__memmove_chk
-  call i8* @__memmove_chk(i8* %dst, i8* %src, i64 2848, i64 1824)
-  ret void
+; CHECK-NEXT: %ret = call i8* @__memmove_chk(i8* bitcast (%struct.T3* @t3 to i8*), i8* bitcast (%struct.T1* @t1 to i8*), i64 2848, i64 1824)
+; CHECK-NEXT: ret i8* %ret
+  %ret = call i8* @__memmove_chk(i8* %dst, i8* %src, i64 2848, i64 1824)
+  ret i8* %ret
 }
 
-define void @test_no_simplify2() {
+define i8* @test_no_simplify2() {
 ; CHECK-LABEL: @test_no_simplify2(
   %dst = bitcast %struct.T1* @t1 to i8*
   %src = bitcast %struct.T2* @t2 to i8*
 
-; CHECK-NEXT: call i8* @__memmove_chk
-  call i8* @__memmove_chk(i8* %dst, i8* %src, i64 1024, i64 0)
-  ret void
+; CHECK-NEXT: %ret = call i8* @__memmove_chk(i8* bitcast (%struct.T1* @t1 to i8*), i8* bitcast (%struct.T2* @t2 to i8*), i64 1024, i64 0)
+; CHECK-NEXT: ret i8* %ret
+  %ret = call i8* @__memmove_chk(i8* %dst, i8* %src, i64 1024, i64 0)
+  ret i8* %ret
 }
 
 declare i8* @__memmove_chk(i8*, i8*, i64, i64)