[llvm] [InstCombine] Add transforms `(icmp spred (and X, Y), X)` if `X` or `Y` are known signed/unsigned (PR #94417)

[via llvm-commits]

================
@@ -4745,6 +4745,40 @@ static Instruction *foldICmpAndXX(ICmpInst &I, const SimplifyQuery &Q,
                           Constant::getNullValue(Op1->getType()));
   }
 
+  if (!ICmpInst::isSigned(Pred))
+    return nullptr;
+
+  KnownBits KnownY = IC.computeKnownBits(A, /*Depth=*/0, &I);
+  // (X & NegY) spred X --> (X & NegY) upred X
+  if (KnownY.isNegative())
----------------
goldsteinn wrote:

It is tests in `Transforms/InstCombine/icmp-of-and-x.ll`.

Without it we get the following regressions:
```
   KnownBits KnownY = IC.computeKnownBits(A, /*Depth=*/0, &I);
   // (X & NegY) spred X --> (X & NegY) upred X
-  if (KnownY.isNegative())
+  if (KnownY.isNegative() && 0)
     return new ICmpInst(ICmpInst::getUnsignedPredicate(Pred), Op0, Op1);
 
   if (Pred != ICmpInst::ICMP_SLE && Pred != ICmpInst::ICMP_SGT)
modified   llvm/test/Transforms/InstCombine/icmp-of-and-x.ll
@@ -58,7 +58,7 @@ define i1 @icmp_sge_x_negy(i8 %x, i8 %y) {
 ; CHECK-NEXT:    [[CY:%.*]] = icmp slt i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[CY]])
 ; CHECK-NEXT:    [[AND:%.*]] = and i8 [[X:%.*]], [[Y]]
-; CHECK-NEXT:    [[Z:%.*]] = icmp eq i8 [[AND]], [[X]]
+; CHECK-NEXT:    [[Z:%.*]] = icmp sge i8 [[AND]], [[X]]
 ; CHECK-NEXT:    ret i1 [[Z]]
 ;
   %cy = icmp slt i8 %y, 0
@@ -74,7 +74,7 @@ define i1 @icmp_slt_x_negy(i8 %x, i8 %y) {
 ; CHECK-NEXT:    br i1 [[CY]], label [[NEGY:%.*]], label [[POSY:%.*]]
 ; CHECK:       negy:
 ; CHECK-NEXT:    [[AND:%.*]] = and i8 [[X:%.*]], [[Y]]
-; CHECK-NEXT:    [[Z:%.*]] = icmp ne i8 [[AND]], [[X]]
+; CHECK-NEXT:    [[Z:%.*]] = icmp slt i8 [[AND]], [[X]]
 ; CHECK-NEXT:    ret i1 [[Z]]
 ; CHECK:       posy:
 ; CHECK-NEXT:    [[R:%.*]] = call i1 @barrier()
@@ -116,7 +116,10 @@ posy:
 
 define i1 @icmp_sle_x_negy(i8 %x, i8 %yy) {
 ; CHECK-LABEL: @icmp_sle_x_negy(
-; CHECK-NEXT:    ret i1 true
+; CHECK-NEXT:    [[Y:%.*]] = or i8 [[YY:%.*]], -128
+; CHECK-NEXT:    [[AND:%.*]] = and i8 [[Y]], [[X:%.*]]
+; CHECK-NEXT:    [[Z:%.*]] = icmp sle i8 [[AND]], [[X]]
+; CHECK-NEXT:    ret i1 [[Z]]
 ;
   %y = or i8 %yy, 128
   %and = and i8 %y, %x
@@ -126,7 +129,10 @@ define i1 @icmp_sle_x_negy(i8 %x, i8 %yy) {
 
 define <2 x i1> @icmp_sgt_x_negy(<2 x i8> %x, <2 x i8> %yy) {
 ; CHECK-LABEL: @icmp_sgt_x_negy(
-; CHECK-NEXT:    ret <2 x i1> zeroinitializer
+; CHECK-NEXT:    [[Y:%.*]] = or <2 x i8> [[YY:%.*]], <i8 -128, i8 -128>
+; CHECK-NEXT:    [[AND:%.*]] = and <2 x i8> [[Y]], [[X:%.*]]
+; CHECK-NEXT:    [[Z:%.*]] = icmp sgt <2 x i8> [[AND]], [[X]]
+; CHECK-NEXT:    ret <2 x i1> [[Z]]
 ;
   %y = or <2 x i8> %yy, <i8 128, i8 128>
   %and = and <2 x i8> %y, %x

```

https://github.com/llvm/llvm-project/pull/94417