Add translation of FPFastMathMode decorations in SPIRVReader. This is a port of KhronosGroup/SPIRV-LLVM-Translator@14e2c5f (2nd try). (#32)

Author: grey-eminence

IGC/AdaptorOCL/SPIRV/SPIRVReader.cpp

@@ -2064,6 +2064,25 @@ SPIRVToLLVM::transConvertInst(SPIRVValue* BV, Function* F, BasicBlock* BB) {
   return ConstantExpr::getCast(CO, dyn_cast<Constant>(Src), Dst);
 }
 
+static void applyFPFastMathModeDecorations(const SPIRVValue* BV,
+    Instruction* Inst) {
+    SPIRVWord V;
+    FastMathFlags FMF;
+    if (BV->hasDecorate(DecorationFPFastMathMode, 0, &V)) {
+        if (V & FPFastMathModeNotNaNMask)
+            FMF.setNoNaNs();
+        if (V & FPFastMathModeNotInfMask)
+            FMF.setNoInfs();
+        if (V & FPFastMathModeNSZMask)
+            FMF.setNoSignedZeros();
+        if (V & FPFastMathModeAllowRecipMask)
+            FMF.setAllowReciprocal();
+        if (V & FPFastMathModeFastMask)
+            FMF.setFast();
+        Inst->setFastMathFlags(FMF);
+    }
+}
+
 BinaryOperator *SPIRVToLLVM::transShiftLogicalBitwiseInst(SPIRVValue* BV,
     BasicBlock* BB,Function* F) {
   SPIRVBinary* BBN = static_cast<SPIRVBinary*>(BV);
@@ -2085,6 +2104,7 @@ BinaryOperator *SPIRVToLLVM::transShiftLogicalBitwiseInst(SPIRVValue* BV,
     Inst->setHasNoUnsignedWrap(true);
   }
 
+  applyFPFastMathModeDecorations(BV, Inst);
   return Inst;
 }
 
@@ -3181,15 +3201,17 @@ SPIRVToLLVM::transValueWithoutDecoration(SPIRVValue *BV, Function *F,
 
   case OpFNegate: {
     SPIRVUnary *BC = static_cast<SPIRVUnary*>(BV);
-    return mapValue(BV,
+    auto Neg =
 #if LLVM_VERSION_MAJOR <= 10
         BinaryOperator
 #else
         UnaryOperator
 #endif
         ::CreateFNeg(
       transValue(BC->getOperand(0), F, BB),
-      BV->getName(), BB));
+      BV->getName(), BB);
+    applyFPFastMathModeDecorations(BV, Neg);
+    return mapValue(BV, Neg);
     }
     break;