[NFC] Add tests for ssubo X, C -> saddo X, -C

[dlrobertson]

Summary

Add baseline tests for canonicalization of
ssubo X, C -> saddo X, -C.

[nikic]

It would be good to also have test cases (for the ssubo->saddo canonicalization, not the nsw fold) where the vector constant argument of the ssubo has undef or is non-splat. This is one of those rare cases where we can easily support them, because the necessary machinery is already in place (see https://github.com/llvm-mirror/llvm/blob/master/lib/Transforms/InstCombine/InstCombineCalls.cpp#L2194).

[nikic]

Additionally we'll also want to test cases where we have i8 -128 on the RHS (with the usual variations, like vector with one element -128 but not others), as we can't do the canonicalization for that case.

[dlrobertson]

In D59653#1438433, @nikic wrote:

It would be good to also have test cases (for the ssubo->saddo canonicalization, not the nsw fold) where the vector constant argument of the ssubo has undef or is non-splat. This is one of those rare cases where we can easily support them, because the necessary machinery is already in place (see https://github.com/llvm-mirror/llvm/blob/master/lib/Transforms/InstCombine/InstCombineCalls.cpp#L2194).

Makes sense.

In D59653#1438673, @nikic wrote:

Additionally we'll also want to test cases where we have i8 -128 on the RHS (with the usual variations, like vector with one element -128 but not others), as we can't do the canonicalization for that case.

Sounds good!

[dlrobertson]

Added test cases

[nikic]

LGTM

llvm/test/Transforms/InstCombine/sadd-with-overflow.ll

 ; CHECK-NEXT:    [[A:%.*]] = add i32 [[X:%.*]], 12
 ; CHECK-NEXT:    [[B:%.*]] = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 [[A]], i32 30)
 ; CHECK-NEXT:    ret { i32, i1 } [[B]]
 ;
   %a = add i32 %x, 12
   %b = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 30, i32 %a)
   ret { i32, i1 } %b
 }
+
+define { i32, i1 } @fold_sub_simple(i32 %x) {
+; CHECK-LABEL: @fold_sub_simple(
+; CHECK-NEXT:    [[TMP1:%.*]] = call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 [[X:%.*]], i32 42)
+; CHECK-NEXT:    ret { i32, i1 } [[TMP1]]
+;
+  %a = sub nsw i32 %x, -12
+  %b = tail call { i32, i1 } @llvm.sadd.with.overflow.i32(i32 %a, i32 30)
+  ret { i32, i1 } %b
+}

llvm/test/Transforms/InstCombine/ssub-with-overflow.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+declare { <2 x i32>, <2 x i1> } @llvm.ssub.with.overflow.v2i32(<2 x i32>, <2 x i32>)
+
+declare { i32, i1 } @llvm.ssub.with.overflow.i32(i32, i32)
+
+declare { i8, i1 } @llvm.ssub.with.overflow.i8(i8, i8)
+
+define { i32, i1 } @simple_fold(i32 %x) {
+; CHECK-LABEL: @simple_fold(
+; CHECK-NEXT:    [[A:%.*]] = add nsw i32 [[X:%.*]], -7
+; CHECK-NEXT:    [[B:%.*]] = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 [[A]], i32 13)
+; CHECK-NEXT:    ret { i32, i1 } [[B]]
+;
+  %a = sub nsw i32 %x, 7
+  %b = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 %a, i32 13)
+  ret { i32, i1 } %b
+}
+
+define { i32, i1 } @fold_mixed_signs(i32 %x) {
+; CHECK-LABEL: @fold_mixed_signs(
+; CHECK-NEXT:    [[A:%.*]] = add nsw i32 [[X:%.*]], -13
+; CHECK-NEXT:    [[B:%.*]] = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 [[A]], i32 -7)
+; CHECK-NEXT:    ret { i32, i1 } [[B]]
+;
+  %a = sub nsw i32 %x, 13
+  %b = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 %a, i32 -7)
+  ret { i32, i1 } %b
+}
+
+define { i8, i1 } @fold_on_constant_sub_no_overflow(i8 %x) {
+; CHECK-LABEL: @fold_on_constant_sub_no_overflow(
+; CHECK-NEXT:    [[A:%.*]] = add nsw i8 [[X:%.*]], -100
+; CHECK-NEXT:    [[B:%.*]] = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 [[A]], i8 28)
+; CHECK-NEXT:    ret { i8, i1 } [[B]]
+;
+  %a = sub nsw i8 %x, 100
+  %b = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 %a, i8 28)
+  ret { i8, i1 } %b
+}
+
+define { i8, i1 } @no_fold_on_constant_sub_overflow(i8 %x) {
+; CHECK-LABEL: @no_fold_on_constant_sub_overflow(
+; CHECK-NEXT:    [[A:%.*]] = add nsw i8 [[X:%.*]], -100
+; CHECK-NEXT:    [[B:%.*]] = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 [[A]], i8 29)
+; CHECK-NEXT:    ret { i8, i1 } [[B]]
+;
+  %a = sub nsw i8 %x, 100
+  %b = tail call { i8, i1 } @llvm.ssub.with.overflow.i8(i8 %a, i8 29)
+  ret { i8, i1 } %b
+}
+
+define { <2 x i32>, <2 x i1> } @fold_simple_splat_constant(<2 x i32> %x) {
+; CHECK-LABEL: @fold_simple_splat_constant(
+; CHECK-NEXT:    [[A:%.*]] = add nsw <2 x i32> [[X:%.*]], <i32 -12, i32 -12>
+; CHECK-NEXT:    [[B:%.*]] = tail call { <2 x i32>, <2 x i1> } @llvm.ssub.with.overflow.v2i32(<2 x i32> [[A]], <2 x i32> <i32 30, i32 30>)
+; CHECK-NEXT:    ret { <2 x i32>, <2 x i1> } [[B]]
+;
+  %a = sub nsw <2 x i32> %x, <i32 12, i32 12>
+  %b = tail call { <2 x i32>, <2 x i1> } @llvm.ssub.with.overflow.v2i32(<2 x i32> %a, <2 x i32> <i32 30, i32 30>)
+  ret { <2 x i32>, <2 x i1> } %b
+}
+
+define { <2 x i32>, <2 x i1> } @no_fold_splat_undef_constant(<2 x i32> %x) {
+; CHECK-LABEL: @no_fold_splat_undef_constant(
+; CHECK-NEXT:    [[A:%.*]] = add <2 x i32> [[X:%.*]], <i32 -12, i32 undef>
+; CHECK-NEXT:    [[B:%.*]] = tail call { <2 x i32>, <2 x i1> } @llvm.ssub.with.overflow.v2i32(<2 x i32> [[A]], <2 x i32> <i32 30, i32 30>)
+; CHECK-NEXT:    ret { <2 x i32>, <2 x i1> } [[B]]
+;
+  %a = sub nsw <2 x i32> %x, <i32 12, i32 undef>
+  %b = tail call { <2 x i32>, <2 x i1> } @llvm.ssub.with.overflow.v2i32(<2 x i32> %a, <2 x i32> <i32 30, i32 30>)
+  ret { <2 x i32>, <2 x i1> } %b
+}
+
+define { <2 x i32>, <2 x i1> } @no_fold_splat_not_constant(<2 x i32> %x, <2 x i32> %y) {
+; CHECK-LABEL: @no_fold_splat_not_constant(
+; CHECK-NEXT:    [[A:%.*]] = sub nsw <2 x i32> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[B:%.*]] = tail call { <2 x i32>, <2 x i1> } @llvm.ssub.with.overflow.v2i32(<2 x i32> [[A]], <2 x i32> <i32 30, i32 30>)
+; CHECK-NEXT:    ret { <2 x i32>, <2 x i1> } [[B]]
+;
+  %a = sub nsw <2 x i32> %x, %y
+  %b = tail call { <2 x i32>, <2 x i1> } @llvm.ssub.with.overflow.v2i32(<2 x i32> %a, <2 x i32> <i32 30, i32 30>)
+  ret { <2 x i32>, <2 x i1> } %b
+}
+
+define { i32, i1 } @fold_nuwnsw(i32 %x) {
+; CHECK-LABEL: @fold_nuwnsw(
+; CHECK-NEXT:    [[A:%.*]] = add nsw i32 [[X:%.*]], -12
+; CHECK-NEXT:    [[B:%.*]] = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 [[A]], i32 30)
+; CHECK-NEXT:    ret { i32, i1 } [[B]]
+;
+  %a = sub nuw nsw i32 %x, 12
+  %b = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 %a, i32 30)
+  ret { i32, i1 } %b
+}
+
+define { i32, i1 } @no_fold_nuw(i32 %x) {
+; CHECK-LABEL: @no_fold_nuw(
+; CHECK-NEXT:    [[A:%.*]] = add i32 [[X:%.*]], -12
+; CHECK-NEXT:    [[B:%.*]] = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 [[A]], i32 30)
+; CHECK-NEXT:    ret { i32, i1 } [[B]]
+;
+  %a = sub nuw i32 %x, 12
+  %b = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 %a, i32 30)
+  ret { i32, i1 } %b
+}
+
+define { i32, i1 } @no_fold_wrapped_sub(i32 %x) {
+; CHECK-LABEL: @no_fold_wrapped_sub(
+; CHECK-NEXT:    [[A:%.*]] = add i32 [[X:%.*]], -12
+; CHECK-NEXT:    [[B:%.*]] = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 30, i32 [[A]])
+; CHECK-NEXT:    ret { i32, i1 } [[B]]
+;
+  %a = sub i32 %x, 12
+  %b = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 30, i32 %a)
+  ret { i32, i1 } %b
+}
+
+define { i32, i1 } @fold_add_simple(i32 %x) {
+; CHECK-LABEL: @fold_add_simple(
+; CHECK-NEXT:    [[A:%.*]] = add nsw i32 [[X:%.*]], -12
+; CHECK-NEXT:    [[B:%.*]] = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 [[A]], i32 30)
+; CHECK-NEXT:    ret { i32, i1 } [[B]]
+;
+  %a = add nsw i32 %x, -12
+  %b = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 %a, i32 30)
+  ret { i32, i1 } %b
+}