[llvm] [X86][GlobalISel] Enable scalar versions of G_UITOFP and G_FPTOUI (PR #100079)

[Simon Pilgrim via llvm-commits]

================
@@ -498,6 +498,64 @@ X86LegalizerInfo::X86LegalizerInfo(const X86Subtarget &STI,
       .clampScalar(0, s32, sMaxScalar)
       .widenScalarToNextPow2(1);
 
+  // For G_UITOFP and G_FPTOUI without AVX512, we have to custom legalize types
+  // <= s32 manually. Otherwise, in custom handler there is no way to
+  // understand whether s32 is an original type and we need to promote it to
+  // s64 or s32 is obtained after widening and we shouldn't widen it to s64.
+  //
+  // For AVX512 we simply widen types as there is direct mapping from opcodes
+  // to asm instructions.
+  getActionDefinitionsBuilder(G_UITOFP)
+      .legalIf([=](const LegalityQuery &Query) {
+        return HasAVX512 && typeInSet(0, {s32, s64})(Query) &&
+               typeInSet(1, {s32, s64})(Query);
+      })
+      .customIf([=](const LegalityQuery &Query) {
+        return !HasAVX512 &&
+               ((HasSSE1 && typeIs(0, s32)(Query)) ||
+                (HasSSE2 && typeIs(0, s64)(Query))) &&
+               (scalarNarrowerThan(1, 32)(Query) ||
+                (Is64Bit && typeIs(1, s32)(Query)));
+      })
+      .lowerIf([=](const LegalityQuery &Query) {
+        // Lower conversions from s64
+        return !HasAVX512 &&
+               ((HasSSE1 && typeIs(0, s32)(Query)) ||
+                (HasSSE2 && typeIs(0, s64)(Query))) &&
+               (Is64Bit && typeIs(1, s64)(Query));
+      })
+      .clampScalar(0, s32, HasSSE2 ? s64 : s32)
+      .widenScalarToNextPow2(0)
+      .clampScalar(1, s32, sMaxScalar)
+      .widenScalarToNextPow2(1);
+
+  getActionDefinitionsBuilder(G_FPTOUI)
+      .legalIf([=](const LegalityQuery &Query) {
+        return HasAVX512 && typeInSet(0, {s32, s64})(Query) &&
+               typeInSet(1, {s32, s64})(Query);
+      })
+      .customIf([=](const LegalityQuery &Query) {
+        return !HasAVX512 &&
+               ((HasSSE1 && typeIs(1, s32)(Query)) ||
+                (HasSSE2 && typeIs(1, s64)(Query))) &&
+               (scalarNarrowerThan(0, 32)(Query) ||
+                (Is64Bit && typeIs(0, s32)(Query)));
----------------
RKSimon wrote:

`scalarNarrowerThan(0, Is64Bit ? 64 : 32)`?

https://github.com/llvm/llvm-project/pull/100079