[ValueTracking] emit a remark when we detect a conflicting assumption (PR31809)

This is a follow-up to D29395 where we try to be good citizens and let the user know that
we've probably gone off the rails.

This should allow us to resolve:
https://llvm.org/bugs/show_bug.cgi?id=31809

Differential Revision: https://reviews.llvm.org/D29404

llvm-svn: 294208

1 files changed, 28 insertions, 5 deletions

diff --git a/llvm/test/Transforms/InstSimplify/assume.ll b/llvm/test/Transforms/InstSimplify/assume.ll
index 4255238126b..66f2120f292 100644
--- a/llvm/test/Transforms/InstSimplify/assume.ll
+++ b/llvm/test/Transforms/InstSimplify/assume.ll
@@ -1,5 +1,10 @@
 ; NOTE: Assertions have been autogenerated by update_test_checks.py
-; RUN: opt -instsimplify -S < %s | FileCheck %s
+; RUN: opt -instsimplify -S < %s 2>&1 -pass-remarks-analysis=.* | FileCheck %s
+
+; Verify that warnings are emitted for the 2nd and 3rd tests.
+
+; CHECK: remark: /tmp/s.c:1:13: Detected conflicting code assumptions.
+; CHECK: remark: /tmp/s.c:4:10: Detected conflicting code assumptions.
 
 define void @test1() {
 ; CHECK-LABEL: @test1(
@@ -15,12 +20,12 @@ define void @test1() {
 ; return value. There's no way to win (we can't undo transforms that happened
 ; based on half-truths), so just don't crash.
 
-define i64 @PR31809() {
+define i64 @PR31809() !dbg !7 {
 ; CHECK-LABEL: @PR31809(
 ; CHECK-NEXT:    ret i64 3
 ;
   %a = alloca i32
-  %t1 = ptrtoint i32* %a to i64
+  %t1 = ptrtoint i32* %a to i64, !dbg !9
   %cond = icmp eq i64 %t1, 3
   call void @llvm.assume(i1 %cond)
   ret i64 %t1
@@ -30,14 +35,14 @@ define i64 @PR31809() {
 ; so just don't crash. The second icmp+assume gets processed later, so that
 ; determines the return value.
 
-define i8 @conflicting_assumptions(i8 %x) {
+define i8 @conflicting_assumptions(i8 %x) !dbg !10 {
 ; CHECK-LABEL: @conflicting_assumptions(
 ; CHECK-NEXT:    call void @llvm.assume(i1 false)
 ; CHECK-NEXT:    [[COND2:%.*]] = icmp eq i8 %x, 4
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[COND2]])
 ; CHECK-NEXT:    ret i8 5
 ;
-  %add = add i8 %x, 1
+  %add = add i8 %x, 1, !dbg !11
   %cond1 = icmp eq i8 %x, 3
   call void @llvm.assume(i1 %cond1)
   %cond2 = icmp eq i8 %x, 4
@@ -47,3 +52,21 @@ define i8 @conflicting_assumptions(i8 %x) {
 
 declare void @llvm.assume(i1) nounwind
 
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 4.0.0 (trunk 282540) (llvm/trunk 282542)", isOptimized: true, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
+!1 = !DIFile(filename: "/tmp/s.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"PIC Level", i32 2}
+!6 = !{!"clang version 4.0.0 (trunk 282540) (llvm/trunk 282542)"}
+!7 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !8, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: true, unit: !0, variables: !2)
+!8 = !DISubroutineType(types: !2)
+!9 = !DILocation(line: 1, column: 13, scope: !7)
+!10 = distinct !DISubprogram(name: "bar", scope: !1, file: !1, line: 3, type: !8, isLocal: false, isDefinition: true, scopeLine: 3, isOptimized: true, unit: !0, variables: !2)
+!11 = !DILocation(line: 4, column: 10, scope: !10)
+!12 = !DILocation(line: 4, column: 3, scope: !10)
+