AMDGPU: Refactor treatment of denormal mode

Start moving towards treating this as a property of the calling
convention, and not the subtarget. The default denormal mode should
not be part of the subtarget, and be moved into a separate function
attribute.

This patch is still NFC. The denormal mode remains as a subtarget
feature for now, but make the necessary changes to switch to using an
attribute.

2 files changed, 21 insertions, 3 deletions

diff --git a/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp b/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
index c72f93eb739..a4b216f583d 100644
--- a/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp
@@ -1303,7 +1303,8 @@ bool splitMUBUFOffset(uint32_t Imm, uint32_t &SOffset, uint32_t &ImmOffset,
   return true;
 }
 
-SIModeRegisterDefaults::SIModeRegisterDefaults(const Function &F) {
+SIModeRegisterDefaults::SIModeRegisterDefaults(const Function &F,
+                                               const GCNSubtarget &ST) {
   *this = getDefaultForCallingConv(F.getCallingConv());
 
   StringRef IEEEAttr = F.getFnAttribute("amdgpu-ieee").getValueAsString();
@@ -1314,6 +1315,9 @@ SIModeRegisterDefaults::SIModeRegisterDefaults(const Function &F) {
     = F.getFnAttribute("amdgpu-dx10-clamp").getValueAsString();
   if (!DX10ClampAttr.empty())
     DX10Clamp = DX10ClampAttr == "true";
+
+  FP32Denormals = ST.hasFP32Denormals(F);
+  FP64FP16Denormals = ST.hasFP64FP16Denormals(F);
 }
 
 namespace {
diff --git a/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.h b/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.h
index f8c082060ff..05bb39235a4 100644
--- a/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.h
+++ b/llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.h
@@ -676,7 +676,8 @@ struct SIModeRegisterDefaults {
     FP32Denormals(true),
     FP64FP16Denormals(true) {}
 
-  SIModeRegisterDefaults(const Function &F);
+  // FIXME: Should not depend on the subtarget
+  SIModeRegisterDefaults(const Function &F, const GCNSubtarget &ST);
 
   static SIModeRegisterDefaults getDefaultForCallingConv(CallingConv::ID CC) {
     const bool IsCompute = AMDGPU::isCompute(CC);
@@ -695,10 +696,23 @@ struct SIModeRegisterDefaults {
            FP64FP16Denormals == Other.FP64FP16Denormals;
   }
 
+  /// Returns true if a flag is compatible if it's enabled in the callee, but
+  /// disabled in the caller.
+  static bool oneWayCompatible(bool CallerMode, bool CalleeMode) {
+    return CallerMode == CalleeMode || (CallerMode && !CalleeMode);
+  }
+
   // FIXME: Inlining should be OK for dx10-clamp, since the caller's mode should
   // be able to override.
   bool isInlineCompatible(SIModeRegisterDefaults CalleeMode) const {
-    return *this == CalleeMode;
+    if (DX10Clamp != CalleeMode.DX10Clamp)
+      return false;
+    if (IEEE != CalleeMode.IEEE)
+      return false;
+
+    // Allow inlining denormals enabled into denormals flushed functions.
+    return oneWayCompatible(FP64FP16Denormals, CalleeMode.FP64FP16Denormals) &&
+           oneWayCompatible(FP32Denormals, CalleeMode.FP32Denormals);
   }
 };