Fix incorrect behavior of operator% (shader-slang#3470)

* Fix incorrect behavior of operator%

Fixes shader-slang#1059.

This change fixes the incorrect translation of "operator%" from
HLSL to SPIRV.

The issue stems from the fact that the behavior of "operator%" in
GLSL differs from that in HLSL. In HLSL it behaves as "remainder"
where as it behaves as "modulus" in GLSL.

We have been using SpvOpFMod for operator% when Slang compiles
from HLSL to SPRIV, which is incorrect.  This change switches it
to SpvOpFRem.

The tests are slightly modified to reveal any potential issues.

* Change output type of test/compute/frem

For testing the operator%, we are using "int" as the output type of the
test, "test/compute/frem.slang".

Since the operands are in float type, it is more preferable to have a
float type as the resulting type. This can be done with an option,
"-output-using-type".

---------

Co-authored-by: Yong He <yonghe@outlook.com>

Author: jkwak-work

source/slang/slang-emit-spirv.cpp

@@ -4398,7 +4398,7 @@ struct SPIRVEmitContext
             opCode = isSigned ? SpvOpSRem : SpvOpUMod;
             break;
         case kIROp_FRem:
-            opCode = SpvOpFMod;
+            opCode = SpvOpFRem;
             break;
         case kIROp_Less:
             opCode = isFloatingPoint ? SpvOpFOrdLessThan

tests/compute/frem.slang

@@ -1,13 +1,13 @@
 // frem.slang
 
-//TEST(compute):COMPARE_COMPUTE: -shaderobj
-//TEST(compute):COMPARE_COMPUTE:-cpu -shaderobj
-//TEST(compute):COMPARE_COMPUTE:-vk -shaderobj
+//TEST(compute):COMPARE_COMPUTE: -shaderobj -output-using-type
+//TEST(compute):COMPARE_COMPUTE:-cpu -shaderobj -output-using-type
+//TEST(compute):COMPARE_COMPUTE:-vk -shaderobj -emit-spirv-directly -output-using-type
 
 // Test uses of floating-point `%` operator.
 
 RWStructuredBuffer<float> gInput;
-//TEST_INPUT:ubuffer(data=[2.0 1.0 5.0 2.0 2.0 -4.0 -5.0 2.0], stride=4):name=gInput
+//TEST_INPUT:ubuffer(data=[2.0 1.0 5.0 2.0 1.0 -4.0 -5.0 4.0], stride=4):name=gInput
 
 int test(int inVal)
 {
@@ -17,7 +17,7 @@ int test(int inVal)
 }
 
 //TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
-RWStructuredBuffer<int> outputBuffer;
+RWStructuredBuffer<float> outputBuffer;
 
 [numthreads(4, 1, 1)]
 void computeMain(int3 dispatchThreadID : SV_DispatchThreadID)
@@ -26,4 +26,4 @@ void computeMain(int3 dispatchThreadID : SV_DispatchThreadID)
 	int inVal = tid;
 	int outVal = test(inVal);
 	outputBuffer[tid] = outVal;
-}
+}

tests/compute/frem.slang.2.expected.txt

@@ -1,4 +1,5 @@
-0
-1
-FFFFFFFE
-1
+type: float
+0.000000
+1.000000
+1.000000
+-1.000000

tests/compute/frem.slang.expected.txt

@@ -1,4 +1,5 @@
-0
-1
-2
-FFFFFFFF
+type: float
+0.000000
+1.000000
+1.000000
+-1.000000