[libclc] [libclc] Refine __clc_fp*_subnormals_supported and __clc_flush_denormal_if_not_supported (PR #157633)

[Matt Arsenault via cfe-commits]

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@@ -127,9 +127,9 @@ _CLC_DEF _CLC_OVERLOAD float __clc_sw_fma(float a, float b, float c) {
     return c;
   }
 
-  a = __clc_flush_denormal_if_not_supported(a);
-  b = __clc_flush_denormal_if_not_supported(b);
-  c = __clc_flush_denormal_if_not_supported(c);
+  a = __clc_soft_flush_denormal(a);
+  b = __clc_soft_flush_denormal(b);
+  c = __clc_soft_flush_denormal(c);
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arsenm wrote:

I think r600 always had FMA, it's just not "fast" on all of them. In any case, the backed is obligated to implement llvm.fma correctly 

https://github.com/llvm/llvm-project/pull/157633