Author: Roman Lebedev Date: 2020-12-18T21:18:13+03:00 New Revision: 9b183a1452c7e5091be01661188b7cb04d842a4c
URL: https://github.com/llvm/llvm-project/commit/9b183a1452c7e5091be01661188b7cb04d842a4c DIFF: https://github.com/llvm/llvm-project/commit/9b183a1452c7e5091be01661188b7cb04d842a4c.diff LOG: [NFC][InstSimplify] Add miscompiled testcase from D87188/D87197 Thanks to Dave Green for producing an actionable reproducer! It is (obviously) a miscompile: ``` ---------------------------------------- define i32 @select_abs_of_abs_eq_wrong(i32 %x, i32 %y) { %0: %abs = abs i32 %x, 0 %neg = sub i32 0, %abs %cmp = icmp eq i32 %y, 0 %sel = select i1 %cmp, i32 %neg, i32 %abs ret i32 %sel } => define i32 @select_abs_of_abs_eq_wrong(i32 %x, i32 %y) { %0: %abs = abs i32 %x, 0 ret i32 %abs } Transformation doesn't verify! ERROR: Value mismatch Example: i32 %x = #xe0000000 (3758096384, -536870912) i32 %y = #x00000000 (0) Source: i32 %abs = #x20000000 (536870912) i32 %neg = #xe0000000 (3758096384, -536870912) i1 %cmp = #x1 (1) i32 %sel = #xe0000000 (3758096384, -536870912) Target: i32 %abs = #x20000000 (536870912) Source value: #xe0000000 (3758096384, -536870912) Target value: #x20000000 (536870912) Alive2: Transform doesn't verify! ``` Added: Modified: llvm/test/Transforms/InstSimplify/abs_intrinsic.ll Removed: ################################################################################ diff --git a/llvm/test/Transforms/InstSimplify/abs_intrinsic.ll b/llvm/test/Transforms/InstSimplify/abs_intrinsic.ll index 4598c5732e12..e0bb1704bc48 100644 --- a/llvm/test/Transforms/InstSimplify/abs_intrinsic.ll +++ b/llvm/test/Transforms/InstSimplify/abs_intrinsic.ll @@ -221,6 +221,19 @@ define i32 @select_abs_of_abs_eq(i32 %x) { ret i32 %sel } +; The comparison is not with the same value we take abs() of, so this isn't the pattern. +define i32 @select_abs_of_abs_eq_wrong(i32 %x, i32 %y) { +; CHECK-LABEL: @select_abs_of_abs_eq_wrong( +; CHECK-NEXT: [[ABS:%.*]] = call i32 @llvm.abs.i32(i32 [[X:%.*]], i1 false) +; CHECK-NEXT: ret i32 [[ABS]] +; + %abs = call i32 @llvm.abs.i32(i32 %x, i1 false) + %neg = sub i32 0, %abs + %cmp = icmp eq i32 %y, 0 ; not %x + %sel = select i1 %cmp, i32 %neg, i32 %abs + ret i32 %sel +} + define i32 @select_abs_of_abs_ne(i32 %x) { ; CHECK-LABEL: @select_abs_of_abs_ne( ; CHECK-NEXT: [[ABS:%.*]] = call i32 @llvm.abs.i32(i32 [[X:%.*]], i1 false) @@ -246,6 +259,20 @@ define i32 @select_nabs_of_abs_eq(i32 %x) { ret i32 %sel } +; The comparison is not with the same value we take abs() of, so this isn't the pattern. +define i32 @select_nabs_of_abs_eq_wrong(i32 %x, i32 %y) { +; CHECK-LABEL: @select_nabs_of_abs_eq_wrong( +; CHECK-NEXT: [[ABS:%.*]] = call i32 @llvm.abs.i32(i32 [[X:%.*]], i1 false) +; CHECK-NEXT: [[NEG:%.*]] = sub i32 0, [[ABS]] +; CHECK-NEXT: ret i32 [[NEG]] +; + %abs = call i32 @llvm.abs.i32(i32 %x, i1 false) + %neg = sub i32 0, %abs + %cmp = icmp eq i32 %y, 0 + %sel = select i1 %cmp, i32 %abs, i32 %neg + ret i32 %sel +} + define i32 @select_nabs_of_abs_ne(i32 %x) { ; CHECK-LABEL: @select_nabs_of_abs_ne( ; CHECK-NEXT: [[ABS:%.*]] = call i32 @llvm.abs.i32(i32 [[X:%.*]], i1 false) _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
