[SelectionDAG] Do not crash on large integers in CheckInteger (#75787)

The CheckInteger routine called from TableGen-generated selection logic
uses getSExtValue - which will abort if the underlying APInt does not
fit into an int64_t.

This case is now triggered by the SystemZ back-end since i128 is a legal
type on certain machines. While we do not have any regular instructions
that take 128-bit immediates (like most other platforms), there are
patterns in the .td files that recognize an i128 "xor ..., -1" as a
"not".

These patterns cause code to be generated that calls the CheckInteger
routine on some i128-valued integer, which may trigger the assert.

Fix by using trySExtValue instead.

Fixes #75710

Author: uweigand

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

@@ -2786,7 +2786,7 @@ CheckInteger(const unsigned char *MatcherTable, unsigned &MatcherIndex,
   Val = decodeSignRotatedValue(Val);
 
   ConstantSDNode *C = dyn_cast<ConstantSDNode>(N);
-  return C && C->getSExtValue() == Val;
+  return C && C->getAPIntValue().trySExtValue() == Val;
 }
 
 LLVM_ATTRIBUTE_ALWAYS_INLINE static bool

llvm/test/CodeGen/SystemZ/xor-09.ll

@@ -15,3 +15,17 @@ define i128 @f1(i128 %a, i128 %b) {
   %res = xor i128 %a, %b
   ret i128 %res
 }
+
+; Verify that xor with a large constant does not crash.
+define i128 @f2(i128 %x) {
+; CHECK-LABEL: f2:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    larl %r1, .LCPI1_0
+; CHECK-NEXT:    vl %v0, 0(%r3), 3
+; CHECK-NEXT:    vl %v1, 0(%r1), 3
+; CHECK-NEXT:    vx %v0, %v0, %v1
+; CHECK-NEXT:    vst %v0, 0(%r2), 3
+; CHECK-NEXT:    br %r14
+  %res = xor i128 %x, 17440380254424117642
+  ret i128 %res
+}