[DXIL] Add frac unary lowering

[farzonl]

This change adds lowering for HLSL's frac intrinsic to DXIL.

This change should complete #70099

[llvmbot]

@llvm/pr-subscribers-backend-directx

Author: Farzon Lotfi (farzonl)

Changes

This change adds lowering for HLSL's frac intrinsic to DXIL.

---

Full diff: https://github.com/llvm/llvm-project/pull/83465.diff

2 Files Affected:

• (modified) llvm/lib/Target/DirectX/DXIL.td (+3)
• (added) llvm/test/CodeGen/DirectX/frac.ll (+43)

diff --git a/llvm/lib/Target/DirectX/DXIL.td b/llvm/lib/Target/DirectX/DXIL.td
index 67ef7986622092..21d1121a956a40 100644
--- a/llvm/lib/Target/DirectX/DXIL.td
+++ b/llvm/lib/Target/DirectX/DXIL.td
@@ -233,3 +233,6 @@ def FlattenedThreadIdInGroup : DXILOpMapping<96, flattenedThreadIdInGroup,
                                              "Provides a flattened index for a "
                                              "given thread within a given "
                                              "group (SV_GroupIndex)">;
+def Frac : DXILOpMapping<22, unary, int_dx_frac,
+                         "Returns a fraction from 0 to 1 that represents the "
+                         "decimal part of the input.">;
diff --git a/llvm/test/CodeGen/DirectX/frac.ll b/llvm/test/CodeGen/DirectX/frac.ll
new file mode 100644
index 00000000000000..d22e062e4e2c4f
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/frac.ll
@@ -0,0 +1,43 @@
+; RUN: opt -S -dxil-op-lower < %s | FileCheck %s
+
+; Make sure dxil operation function calls for frac are generated for float and half.
+; CHECK:call float @dx.op.unary.f32(i32 22, float %{{.*}})
+; CHECK:call half @dx.op.unary.f16(i32 22, half %{{.*}})
+
+target datalayout = "e-m:e-p:32:32-i1:32-i8:8-i16:16-i32:32-i64:64-f16:16-f32:32-f64:64-n8:16:32:64"
+target triple = "dxil-pc-shadermodel6.7-library"
+
+; Function Attrs: noinline nounwind optnone
+define noundef float @_Z3foof(float noundef %a) #0 {
+entry:
+  %a.addr = alloca float, align 4
+  store float %a, ptr %a.addr, align 4
+  %0 = load float, ptr %a.addr, align 4
+  %dx.frac = call float @llvm.dx.frac.f32(float %0)
+  ret float %dx.frac
+}
+
+; Function Attrs: nocallback nofree nosync nounwind readnone speculatable willreturn
+declare float @llvm.dx.frac.f32(float) #1
+
+; Function Attrs: noinline nounwind optnone
+define noundef half @_Z3barDh(half noundef %a) #0 {
+entry:
+  %a.addr = alloca half, align 2
+  store half %a, ptr %a.addr, align 2
+  %0 = load half, ptr %a.addr, align 2
+  %dx.frac = call half @llvm.dx.frac.f16(half %0)
+  ret half %dx.frac
+}
+
+; Function Attrs: nocallback nofree nosync nounwind readnone speculatable willreturn
+declare half @llvm.dx.frac.f16(half) #1
+
+attributes #0 = { noinline nounwind optnone "frame-pointer"="none" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+attributes #1 = { nocallback nofree nosync nounwind readnone speculatable willreturn }
+
+!llvm.module.flags = !{!0}
+!llvm.ident = !{!1}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{!"clang version 15.0.0 (https://github.com/llvm/llvm-project.git 73417c517644db5c419c85c0b3cb6750172fcab5)"}