[CodeGen] Use the common semantic for fixed-point codegen, not the result semantic.

[ebevhan]

Summary

Using the result semantic is wrong in some cases, such as
unsigned fixed-point + signed integer. In this case, the
result semantic is unsigned and the common semantic is
signed.

[leonardchan]

LGTM. Thanks for the fix.

clang/lib/CodeGen/CGExprScalar.cpp

Value *ScalarExprEmitter::EmitFixedPointBinOp(const BinOpInfo &op) {
   Value *FullRHS = EmitFixedPointConversion(RHS, RHSFixedSema, CommonFixedSema,
                                             op.E->getExprLoc());
 
   // Perform the actual operation.
   Value *Result;
   switch (op.Opcode) {
   case BO_AddAssign:
   case BO_Add: {
-    if (ResultFixedSema.isSaturated()) {
-      llvm::Intrinsic::ID IID = ResultFixedSema.isSigned()
+    if (CommonFixedSema.isSaturated()) {
+      llvm::Intrinsic::ID IID = CommonFixedSema.isSigned()
                                     ? llvm::Intrinsic::sadd_sat
                                     : llvm::Intrinsic::uadd_sat;
       Result = Builder.CreateBinaryIntrinsic(IID, FullLHS, FullRHS);
     } else {
       Result = Builder.CreateAdd(FullLHS, FullRHS);
     }
     break;
   }
   case BO_SubAssign:
   case BO_Sub: {
-    if (ResultFixedSema.isSaturated()) {
-      llvm::Intrinsic::ID IID = ResultFixedSema.isSigned()
+    if (CommonFixedSema.isSaturated()) {
+      llvm::Intrinsic::ID IID = CommonFixedSema.isSigned()
                                     ? llvm::Intrinsic::ssub_sat
                                     : llvm::Intrinsic::usub_sat;
       Result = Builder.CreateBinaryIntrinsic(IID, FullLHS, FullRHS);
     } else {
       Result = Builder.CreateSub(FullLHS, FullRHS);
     }
     break;
   }
   case BO_MulAssign:
   case BO_Mul: {
     llvm::Intrinsic::ID IID;
-    if (ResultFixedSema.isSaturated())
-      IID = ResultFixedSema.isSigned()
-                ? llvm::Intrinsic::smul_fix_sat
+    if (CommonFixedSema.isSaturated())
+      IID = CommonFixedSema.isSigned() ? llvm::Intrinsic::smul_fix_sat
                                        : llvm::Intrinsic::umul_fix_sat;
     else
-      IID = ResultFixedSema.isSigned()
-                ? llvm::Intrinsic::smul_fix
+      IID = CommonFixedSema.isSigned() ? llvm::Intrinsic::smul_fix
                                        : llvm::Intrinsic::umul_fix;
     Result = Builder.CreateIntrinsic(IID, {FullLHS->getType()},
         {FullLHS, FullRHS, Builder.getInt32(CommonFixedSema.getScale())});
     break;
   }
   case BO_DivAssign:
   case BO_Div: {
     llvm::Intrinsic::ID IID;
-    if (ResultFixedSema.isSaturated())
-      IID = ResultFixedSema.isSigned() ? llvm::Intrinsic::sdiv_fix_sat
+    if (CommonFixedSema.isSaturated())
+      IID = CommonFixedSema.isSigned() ? llvm::Intrinsic::sdiv_fix_sat
                                        : llvm::Intrinsic::udiv_fix_sat;
     else
-      IID = ResultFixedSema.isSigned() ? llvm::Intrinsic::sdiv_fix
+      IID = CommonFixedSema.isSigned() ? llvm::Intrinsic::sdiv_fix
                                        : llvm::Intrinsic::udiv_fix;
     Result = Builder.CreateIntrinsic(IID, {FullLHS->getType()},
         {FullLHS, FullRHS, Builder.getInt32(CommonFixedSema.getScale())});
     break;    
   }
   case BO_LT:
     return CommonFixedSema.isSigned() ? Builder.CreateICmpSLT(FullLHS, FullRHS)
                                       : Builder.CreateICmpULT(FullLHS, FullRHS);

clang/test/Frontend/fixed_point_add.c

void SaturatedAddition() {
   // UNSIGNED-NEXT: store i16 [[SUM_EXT]], i16* %uf_sat, align 2
   uf_sat = uf_sat + uf_sat;
 
   // CHECK:      [[USA_SAT:%[0-9]+]] = load i16, i16* %usa_sat, align 2
   // CHECK-NEXT: [[I:%[0-9]+]] = load i32, i32* %i, align 4
   // SIGNED-NEXT: [[USA_SAT_RESIZE:%[a-z0-9]+]] = zext i16 [[USA_SAT]] to i40
   // SIGNED-NEXT: [[I_RESIZE:%[a-z0-9]+]] = sext i32 [[I]] to i40
   // SIGNED-NEXT: [[I_UPSCALE:%[a-z0-9]+]] = shl i40 [[I_RESIZE]], 8
-  // SIGNED-NEXT: [[SUM:%[0-9]+]] = call i40 @llvm.uadd.sat.i40(i40 [[USA_SAT_RESIZE]], i40 [[I_UPSCALE]])
+  // SIGNED-NEXT: [[SUM:%[0-9]+]] = call i40 @llvm.sadd.sat.i40(i40 [[USA_SAT_RESIZE]], i40 [[I_UPSCALE]])
   // SIGNED-NEXT: [[USE_MAX:%[0-9]+]] = icmp sgt i40 [[SUM]], 65535
   // SIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = select i1 [[USE_MAX]], i40 65535, i40 [[SUM]]
   // SIGNED-NEXT: [[USE_MIN:%[0-9]+]] = icmp slt i40 [[RESULT]], 0
   // SIGNED-NEXT: [[RESULT2:%[a-z0-9]+]] = select i1 [[USE_MIN]], i40 0, i40 [[RESULT]]
   // SIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = trunc i40 [[RESULT2]] to i16
   // UNSIGNED-NEXT: [[USA_SAT_RESIZE:%[a-z0-9]+]] = zext i16 [[USA_SAT]] to i39
   // UNSIGNED-NEXT: [[I_RESIZE:%[a-z0-9]+]] = sext i32 [[I]] to i39
   // UNSIGNED-NEXT: [[I_UPSCALE:%[a-z0-9]+]] = shl i39 [[I_RESIZE]], 7
-  // UNSIGNED-NEXT: [[SUM:%[0-9]+]] = call i39 @llvm.uadd.sat.i39(i39 [[USA_SAT_RESIZE]], i39 [[I_UPSCALE]])
+  // UNSIGNED-NEXT: [[SUM:%[0-9]+]] = call i39 @llvm.sadd.sat.i39(i39 [[USA_SAT_RESIZE]], i39 [[I_UPSCALE]])
   // UNSIGNED-NEXT: [[USE_MAX:%[0-9]+]] = icmp sgt i39 [[SUM]], 32767
   // UNSIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = select i1 [[USE_MAX]], i39 32767, i39 [[SUM]]
   // UNSIGNED-NEXT: [[USE_MIN:%[0-9]+]] = icmp slt i39 [[RESULT]], 0
   // UNSIGNED-NEXT: [[RESULT2:%[a-z0-9]+]] = select i1 [[USE_MIN]], i39 0, i39 [[RESULT]]
   // UNSIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = trunc i39 [[RESULT2]] to i16
   // CHECK-NEXT: store i16 [[RESULT]], i16* %usa_sat, align 2
   usa_sat = usa_sat + i;
 }

clang/test/Frontend/fixed_point_div.c

void IntDivision() {
   // CHECK-NEXT:    store i16 [[RESIZE6]], i16* %sa, align 2
   sa = sa / ui;
 
   // CHECK:         [[TMP6:%.*]] = load i16, i16* %usa, align 2
   // CHECK-NEXT:    [[TMP7:%.*]] = load i32, i32* %i, align 4
   // SIGNED-NEXT:   [[RESIZE7:%.*]] = zext i16 [[TMP6]] to i40
   // SIGNED-NEXT:   [[RESIZE8:%.*]] = sext i32 [[TMP7]] to i40
   // SIGNED-NEXT:   [[UPSCALE9:%.*]] = shl i40 [[RESIZE8]], 8
-  // SIGNED-NEXT:   [[TMP8:%.*]] = call i40 @llvm.udiv.fix.i40(i40 [[RESIZE7]], i40 [[UPSCALE9]], i32 8)
+  // SIGNED-NEXT:   [[TMP8:%.*]] = call i40 @llvm.sdiv.fix.i40(i40 [[RESIZE7]], i40 [[UPSCALE9]], i32 8)
   // SIGNED-NEXT:   [[RESIZE10:%.*]] = trunc i40 [[TMP8]] to i16
   // UNSIGNED-NEXT: [[RESIZE7:%.*]] = zext i16 [[TMP6]] to i39
   // UNSIGNED-NEXT: [[RESIZE8:%.*]] = sext i32 [[TMP7]] to i39
   // UNSIGNED-NEXT: [[UPSCALE9:%.*]] = shl i39 [[RESIZE8]], 7
-  // UNSIGNED-NEXT: [[TMP8:%.*]] = call i39 @llvm.udiv.fix.i39(i39 [[RESIZE7]], i39 [[UPSCALE9]], i32 7)
+  // UNSIGNED-NEXT: [[TMP8:%.*]] = call i39 @llvm.sdiv.fix.i39(i39 [[RESIZE7]], i39 [[UPSCALE9]], i32 7)
   // UNSIGNED-NEXT: [[RESIZE10:%.*]] = trunc i39 [[TMP8]] to i16
   // CHECK-NEXT:    store i16 [[RESIZE10]], i16* %usa, align 2
   usa = usa / i;
 
   // CHECK:         [[TMP9:%.*]] = load i16, i16* %usa, align 2
   // CHECK-NEXT:    [[TMP10:%.*]] = load i32, i32* %ui, align 4
   // SIGNED-NEXT:   [[RESIZE11:%.*]] = zext i16 [[TMP9]] to i40
   // SIGNED-NEXT:   [[RESIZE12:%.*]] = zext i32 [[TMP10]] to i40
void SaturatedDivision() {
   // UNSIGNED-NEXT: store i16 [[SUM_EXT]], i16* %uf_sat, align 2
   uf_sat = uf_sat / uf_sat;
 
   // CHECK:      [[USA_SAT:%[0-9]+]] = load i16, i16* %usa_sat, align 2
   // CHECK-NEXT: [[I:%[0-9]+]] = load i32, i32* %i, align 4
   // SIGNED-NEXT: [[USA_SAT_RESIZE:%[a-z0-9]+]] = zext i16 [[USA_SAT]] to i40
   // SIGNED-NEXT: [[I_RESIZE:%[a-z0-9]+]] = sext i32 [[I]] to i40
   // SIGNED-NEXT: [[I_UPSCALE:%[a-z0-9]+]] = shl i40 [[I_RESIZE]], 8
-  // SIGNED-NEXT: [[SUM:%[0-9]+]] = call i40 @llvm.udiv.fix.sat.i40(i40 [[USA_SAT_RESIZE]], i40 [[I_UPSCALE]], i32 8)
+  // SIGNED-NEXT: [[SUM:%[0-9]+]] = call i40 @llvm.sdiv.fix.sat.i40(i40 [[USA_SAT_RESIZE]], i40 [[I_UPSCALE]], i32 8)
   // SIGNED-NEXT: [[USE_MAX:%[0-9]+]] = icmp sgt i40 [[SUM]], 65535
   // SIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = select i1 [[USE_MAX]], i40 65535, i40 [[SUM]]
   // SIGNED-NEXT: [[USE_MIN:%[0-9]+]] = icmp slt i40 [[RESULT]], 0
   // SIGNED-NEXT: [[RESULT2:%[a-z0-9]+]] = select i1 [[USE_MIN]], i40 0, i40 [[RESULT]]
   // SIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = trunc i40 [[RESULT2]] to i16
   // UNSIGNED-NEXT: [[USA_SAT_RESIZE:%[a-z0-9]+]] = zext i16 [[USA_SAT]] to i39
   // UNSIGNED-NEXT: [[I_RESIZE:%[a-z0-9]+]] = sext i32 [[I]] to i39
   // UNSIGNED-NEXT: [[I_UPSCALE:%[a-z0-9]+]] = shl i39 [[I_RESIZE]], 7
-  // UNSIGNED-NEXT: [[SUM:%[0-9]+]] = call i39 @llvm.udiv.fix.sat.i39(i39 [[USA_SAT_RESIZE]], i39 [[I_UPSCALE]], i32 7)
+  // UNSIGNED-NEXT: [[SUM:%[0-9]+]] = call i39 @llvm.sdiv.fix.sat.i39(i39 [[USA_SAT_RESIZE]], i39 [[I_UPSCALE]], i32 7)
   // UNSIGNED-NEXT: [[USE_MAX:%[0-9]+]] = icmp sgt i39 [[SUM]], 32767
   // UNSIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = select i1 [[USE_MAX]], i39 32767, i39 [[SUM]]
   // UNSIGNED-NEXT: [[USE_MIN:%[0-9]+]] = icmp slt i39 [[RESULT]], 0
   // UNSIGNED-NEXT: [[RESULT2:%[a-z0-9]+]] = select i1 [[USE_MIN]], i39 0, i39 [[RESULT]]
   // UNSIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = trunc i39 [[RESULT2]] to i16
   // CHECK-NEXT: store i16 [[RESULT]], i16* %usa_sat, align 2
   usa_sat = usa_sat / i;
 }

clang/test/Frontend/fixed_point_mul.c

void IntMultiplication() {
   // CHECK-NEXT:    store i16 [[RESIZE6]], i16* %sa, align 2
   sa = sa * ui;
 
   // CHECK:         [[TMP6:%.*]] = load i16, i16* %usa, align 2
   // CHECK-NEXT:    [[TMP7:%.*]] = load i32, i32* %i, align 4
   // SIGNED-NEXT:   [[RESIZE7:%.*]] = zext i16 [[TMP6]] to i40
   // SIGNED-NEXT:   [[RESIZE8:%.*]] = sext i32 [[TMP7]] to i40
   // SIGNED-NEXT:   [[UPSCALE9:%.*]] = shl i40 [[RESIZE8]], 8
-  // SIGNED-NEXT:   [[TMP8:%.*]] = call i40 @llvm.umul.fix.i40(i40 [[RESIZE7]], i40 [[UPSCALE9]], i32 8)
+  // SIGNED-NEXT:   [[TMP8:%.*]] = call i40 @llvm.smul.fix.i40(i40 [[RESIZE7]], i40 [[UPSCALE9]], i32 8)
   // SIGNED-NEXT:   [[RESIZE10:%.*]] = trunc i40 [[TMP8]] to i16
   // UNSIGNED-NEXT: [[RESIZE7:%.*]] = zext i16 [[TMP6]] to i39
   // UNSIGNED-NEXT: [[RESIZE8:%.*]] = sext i32 [[TMP7]] to i39
   // UNSIGNED-NEXT: [[UPSCALE9:%.*]] = shl i39 [[RESIZE8]], 7
-  // UNSIGNED-NEXT: [[TMP8:%.*]] = call i39 @llvm.umul.fix.i39(i39 [[RESIZE7]], i39 [[UPSCALE9]], i32 7)
+  // UNSIGNED-NEXT: [[TMP8:%.*]] = call i39 @llvm.smul.fix.i39(i39 [[RESIZE7]], i39 [[UPSCALE9]], i32 7)
   // UNSIGNED-NEXT: [[RESIZE10:%.*]] = trunc i39 [[TMP8]] to i16
   // CHECK-NEXT:    store i16 [[RESIZE10]], i16* %usa, align 2
   usa = usa * i;
 
   // CHECK:         [[TMP9:%.*]] = load i16, i16* %usa, align 2
   // CHECK-NEXT:    [[TMP10:%.*]] = load i32, i32* %ui, align 4
   // SIGNED-NEXT:   [[RESIZE11:%.*]] = zext i16 [[TMP9]] to i40
   // SIGNED-NEXT:   [[RESIZE12:%.*]] = zext i32 [[TMP10]] to i40
void SaturatedMultiplication() {
   // UNSIGNED-NEXT: store i16 [[SUM_EXT]], i16* %uf_sat, align 2
   uf_sat = uf_sat * uf_sat;
 
   // CHECK:      [[USA_SAT:%[0-9]+]] = load i16, i16* %usa_sat, align 2
   // CHECK-NEXT: [[I:%[0-9]+]] = load i32, i32* %i, align 4
   // SIGNED-NEXT: [[USA_SAT_RESIZE:%[a-z0-9]+]] = zext i16 [[USA_SAT]] to i40
   // SIGNED-NEXT: [[I_RESIZE:%[a-z0-9]+]] = sext i32 [[I]] to i40
   // SIGNED-NEXT: [[I_UPSCALE:%[a-z0-9]+]] = shl i40 [[I_RESIZE]], 8
-  // SIGNED-NEXT: [[SUM:%[0-9]+]] = call i40 @llvm.umul.fix.sat.i40(i40 [[USA_SAT_RESIZE]], i40 [[I_UPSCALE]], i32 8)
+  // SIGNED-NEXT: [[SUM:%[0-9]+]] = call i40 @llvm.smul.fix.sat.i40(i40 [[USA_SAT_RESIZE]], i40 [[I_UPSCALE]], i32 8)
   // SIGNED-NEXT: [[USE_MAX:%[0-9]+]] = icmp sgt i40 [[SUM]], 65535
   // SIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = select i1 [[USE_MAX]], i40 65535, i40 [[SUM]]
   // SIGNED-NEXT: [[USE_MIN:%[0-9]+]] = icmp slt i40 [[RESULT]], 0
   // SIGNED-NEXT: [[RESULT2:%[a-z0-9]+]] = select i1 [[USE_MIN]], i40 0, i40 [[RESULT]]
   // SIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = trunc i40 [[RESULT2]] to i16
   // UNSIGNED-NEXT: [[USA_SAT_RESIZE:%[a-z0-9]+]] = zext i16 [[USA_SAT]] to i39
   // UNSIGNED-NEXT: [[I_RESIZE:%[a-z0-9]+]] = sext i32 [[I]] to i39
   // UNSIGNED-NEXT: [[I_UPSCALE:%[a-z0-9]+]] = shl i39 [[I_RESIZE]], 7
-  // UNSIGNED-NEXT: [[SUM:%[0-9]+]] = call i39 @llvm.umul.fix.sat.i39(i39 [[USA_SAT_RESIZE]], i39 [[I_UPSCALE]], i32 7)
+  // UNSIGNED-NEXT: [[SUM:%[0-9]+]] = call i39 @llvm.smul.fix.sat.i39(i39 [[USA_SAT_RESIZE]], i39 [[I_UPSCALE]], i32 7)
   // UNSIGNED-NEXT: [[USE_MAX:%[0-9]+]] = icmp sgt i39 [[SUM]], 32767
   // UNSIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = select i1 [[USE_MAX]], i39 32767, i39 [[SUM]]
   // UNSIGNED-NEXT: [[USE_MIN:%[0-9]+]] = icmp slt i39 [[RESULT]], 0
   // UNSIGNED-NEXT: [[RESULT2:%[a-z0-9]+]] = select i1 [[USE_MIN]], i39 0, i39 [[RESULT]]
   // UNSIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = trunc i39 [[RESULT2]] to i16
   // CHECK-NEXT: store i16 [[RESULT]], i16* %usa_sat, align 2
   usa_sat = usa_sat * i;
 }

clang/test/Frontend/fixed_point_sub.c

void SaturatedSubtraction() {
   // UNSIGNED-NEXT: store i16 [[SUM_EXT]], i16* %uf_sat, align 2
   uf_sat = uf_sat - uf_sat;
 
   // CHECK:      [[USA_SAT:%[0-9]+]] = load i16, i16* %usa_sat, align 2
   // CHECK-NEXT: [[I:%[0-9]+]] = load i32, i32* %i, align 4
   // SIGNED-NEXT: [[USA_SAT_RESIZE:%[a-z0-9]+]] = zext i16 [[USA_SAT]] to i40
   // SIGNED-NEXT: [[I_RESIZE:%[a-z0-9]+]] = sext i32 [[I]] to i40
   // SIGNED-NEXT: [[I_UPSCALE:%[a-z0-9]+]] = shl i40 [[I_RESIZE]], 8
-  // SIGNED-NEXT: [[SUM:%[0-9]+]] = call i40 @llvm.usub.sat.i40(i40 [[USA_SAT_RESIZE]], i40 [[I_UPSCALE]])
+  // SIGNED-NEXT: [[SUM:%[0-9]+]] = call i40 @llvm.ssub.sat.i40(i40 [[USA_SAT_RESIZE]], i40 [[I_UPSCALE]])
   // SIGNED-NEXT: [[USE_MAX:%[0-9]+]] = icmp sgt i40 [[SUM]], 65535
   // SIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = select i1 [[USE_MAX]], i40 65535, i40 [[SUM]]
   // SIGNED-NEXT: [[USE_MIN:%[0-9]+]] = icmp slt i40 [[RESULT]], 0
   // SIGNED-NEXT: [[RESULT2:%[a-z0-9]+]] = select i1 [[USE_MIN]], i40 0, i40 [[RESULT]]
   // SIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = trunc i40 [[RESULT2]] to i16
   // UNSIGNED-NEXT: [[USA_SAT_RESIZE:%[a-z0-9]+]] = zext i16 [[USA_SAT]] to i39
   // UNSIGNED-NEXT: [[I_RESIZE:%[a-z0-9]+]] = sext i32 [[I]] to i39
   // UNSIGNED-NEXT: [[I_UPSCALE:%[a-z0-9]+]] = shl i39 [[I_RESIZE]], 7
-  // UNSIGNED-NEXT: [[SUM:%[0-9]+]] = call i39 @llvm.usub.sat.i39(i39 [[USA_SAT_RESIZE]], i39 [[I_UPSCALE]])
+  // UNSIGNED-NEXT: [[SUM:%[0-9]+]] = call i39 @llvm.ssub.sat.i39(i39 [[USA_SAT_RESIZE]], i39 [[I_UPSCALE]])
   // UNSIGNED-NEXT: [[USE_MAX:%[0-9]+]] = icmp sgt i39 [[SUM]], 32767
   // UNSIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = select i1 [[USE_MAX]], i39 32767, i39 [[SUM]]
   // UNSIGNED-NEXT: [[USE_MIN:%[0-9]+]] = icmp slt i39 [[RESULT]], 0
   // UNSIGNED-NEXT: [[RESULT2:%[a-z0-9]+]] = select i1 [[USE_MIN]], i39 0, i39 [[RESULT]]
   // UNSIGNED-NEXT: [[RESULT:%[a-z0-9]+]] = trunc i39 [[RESULT2]] to i16
   // CHECK-NEXT: store i16 [[RESULT]], i16* %usa_sat, align 2
   usa_sat = usa_sat - i;
 }