[clang] [X86][Clang] Add constexpr support for _mm_min_ss/_mm_max_ss/_mm_min_sd/_mm_max_sd/_mm_min_sh/_mm_max_sh intrinsics (PR #178029)

[Simon Pilgrim via cfe-commits]

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@@ -5832,6 +5875,48 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const CallExpr *Call,
           return llvm::minimum(A, B);
         });
 
+  case clang::X86::BI__builtin_ia32_minss:
+  case clang::X86::BI__builtin_ia32_minsd:
+  case clang::X86::BI__builtin_ia32_minsh:
+    return interp__builtin_elementwise_fp_binop(
+        S, OpPC, Call,
+        [](const APFloat &A, const APFloat &B,
+           std::optional<APSInt> RoundingMode) -> std::optional<APFloat> {
+          // Default to _MM_FROUND_CUR_DIRECTION (4) if no rounding mode
+          // specified
+          APSInt DefaultMode(APInt(32, 4), /*isUnsigned=*/true);
+          if (RoundingMode.value_or(DefaultMode) != 4)
+            return std::nullopt;
+          if (A.isNaN() || A.isInfinity() || A.isDenormal() || B.isNaN() ||
+              B.isInfinity() || B.isDenormal())
+            return std::nullopt;
+          if (A.isZero() && B.isZero())
+            return B;
+          return llvm::minimum(A, B);
+        },
+        /*IsScalar=*/true);
+
+  case clang::X86::BI__builtin_ia32_minsh_round_mask:
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RKSimon wrote:

Can we handle AVX512F BI__builtin_ia32_maxsd_round_mask etc. as well with this?

https://github.com/llvm/llvm-project/pull/178029