intrinsic management for fast math sub flags

[mcberg2017]

Summary

This patch addresses handling fast math flags for intrinsics and is malleable enough to provide support for new intrinsics with little or no changes after the fact.

[mcberg2017]

lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

5549

Minor clean up on the braces, it will be in the next upload.

[mcberg2017]

Minor update with some cleanup

[mcberg2017]

Updated for recent changes in the scope of this review...

[mcberg2017]

updated to use the convenience function in r332155

[mcberg2017]

Any other comments on these changes? It would be great to proceed.

[spatel]

In D46563#1098394, @mcberg2017 wrote:

Any other comments on these changes? It would be great to proceed.

I'm still not sold on this approach. IIUC, we're still missing propagation on fcmp, vector reduce, and libcalls.

As I mentioned in D46483, D37686 had a more complete implementation. I drafted a much simpler version of that patch locally. Let me add some tests and clean that up a bit and see if that looks better to you.

lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

void SelectionDAGBuilder::visitTargetIntrinsic(const CallInst &I,
 
   if (!I.getType()->isVoidTy()) {
     if (VectorType *PTy = dyn_cast<VectorType>(I.getType())) {
       EVT VT = TLI.getValueType(DAG.getDataLayout(), PTy);
       Result = DAG.getNode(ISD::BITCAST, getCurSDLoc(), VT, Result);
     } else
       Result = lowerRangeToAssertZExt(DAG, I, Result);
 
+    if (I.getType()->isFloatTy()) {
+      FastMathFlags FMF = I.getFastMathFlags();
+      SDNodeFlags Flags;
+      Flags.setAllowReciprocal(FMF.allowReciprocal());
+      Flags.setAllowContract(FMF.allowContract());
+      Flags.setNoInfs(FMF.noInfs());
+      Flags.setNoNaNs(FMF.noNaNs());
+      Flags.setNoSignedZeros(FMF.noSignedZeros());
+      Flags.setApproximateFuncs(FMF.approxFunc());
+      Flags.setAllowReassociation(FMF.allowReassoc());
+      Result->setFlags(Flags);
+    }
     setValue(&I, Result);
   }
 }
 
 /// GetSignificand - Get the significand and build it into a floating-point
 /// number with exponent of 1:
 ///
 ///   Op = (Op & 0x007fffff) | 0x3f800000;
case Intrinsic::maxnum: {
     return nullptr;
   }
   case Intrinsic::copysign:
     setValue(&I, DAG.getNode(ISD::FCOPYSIGN, sdl,
                              getValue(I.getArgOperand(0)).getValueType(),
                              getValue(I.getArgOperand(0)),
                              getValue(I.getArgOperand(1))));
     return nullptr;
   case Intrinsic::fma:
     setValue(&I, DAG.getNode(ISD::FMA, sdl,
                              getValue(I.getArgOperand(0)).getValueType(),
                              getValue(I.getArgOperand(0)),
                              getValue(I.getArgOperand(1)),
                              getValue(I.getArgOperand(2))));
     return nullptr;
   case Intrinsic::experimental_constrained_fadd:
   case Intrinsic::experimental_constrained_fsub:
if (F->isDeclaration()) {
       // Is this an LLVM intrinsic or a target-specific intrinsic?
       unsigned IID = F->getIntrinsicID();
       if (!IID)
         if (const TargetIntrinsicInfo *II = TM.getIntrinsicInfo())
           IID = II->getIntrinsicID(F);
 
       if (IID) {
         RenameFn = visitIntrinsicCall(I, IID);
-        if (!RenameFn)
+        if (!RenameFn) {
+          if (I.getType()->isFloatTy()) {
+            SDNodeFlags Flags;
+            FastMathFlags FMF = I.getFastMathFlags();
+            Flags.setAllowReciprocal(FMF.allowReciprocal());
+            Flags.setAllowContract(FMF.allowContract());
+            Flags.setNoInfs(FMF.noInfs());
+            Flags.setNoNaNs(FMF.noNaNs());
+            Flags.setNoSignedZeros(FMF.noSignedZeros());
+            Flags.setApproximateFuncs(FMF.approxFunc());
+            Flags.setAllowReassociation(FMF.allowReassoc());
+            SDValue Res = getValue(&I);
+            Res->setFlags(Flags);
+          }
           return;
         }
       }
+    }
 
     // Check for well-known libc/libm calls.  If the function is internal, it
     // can't be a library call.  Don't do the check if marked as nobuiltin for
     // some reason or the call site requires strict floating point semantics.
     LibFunc Func;
     if (!I.isNoBuiltin() && !I.isStrictFP() && !F->hasLocalLinkage() &&
         F->hasName() && LibInfo->getLibFunc(*F, Func) &&
         LibInfo->hasOptimizedCodeGen(Func)) {

test/CodeGen/PowerPC/fmf-propagation.ll

; GLOBAL-NEXT:    blr
   %add = fadd fast float %mul, %z
   ret float %add
 }
 
 ; fma(X, 7.0, X * 42.0) --> X * 49.0
 ; This is the minimum FMF needed for this transform - the FMA allows reassociation.
 
 ; FMFDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'fmul_fma_reassoc1:'
-; FMFDEBUG:         fma {{t[0-9]+}}
+; FMFDEBUG:         fma reassoc {{t[0-9]+}}
 ; FMFDEBUG:       Type-legalized selection DAG: %bb.0 'fmul_fma_reassoc1:'
 
 ; GLOBALDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'fmul_fma_reassoc1:'
 ; GLOBALDEBUG:         fmul reassoc {{t[0-9]+}}
 ; GLOBALDEBUG:       Type-legalized selection DAG: %bb.0 'fmul_fma_reassoc1:'
 
 define float @fmul_fma_reassoc1(float %x) {
 ; FMF-LABEL: fmul_fma_reassoc1:
; GLOBAL-NEXT:    blr
   %mul = fmul float %x, 42.0
   %fma = call reassoc float @llvm.fma.f32(float %x, float 7.0, float %mul)
   ret float %fma
 }
 
 ; This shouldn't change anything - the intermediate fmul result is now also flagged.
 
 ; FMFDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'fmul_fma_reassoc2:'
-; FMFDEBUG:         fma {{t[0-9]+}}
+; FMFDEBUG:         fma reassoc {{t[0-9]+}}
 ; FMFDEBUG:       Type-legalized selection DAG: %bb.0 'fmul_fma_reassoc2:'
 
 ; GLOBALDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'fmul_fma_reassoc2:'
 ; GLOBALDEBUG:         fmul reassoc {{t[0-9]+}}
 ; GLOBALDEBUG:       Type-legalized selection DAG: %bb.0 'fmul_fma_reassoc2:'
 
 define float @fmul_fma_reassoc2(float %x) {
 ; FMF-LABEL: fmul_fma_reassoc2:
; GLOBAL-NEXT:    blr
   %mul = fmul reassoc float %x, 42.0
   %fma = call reassoc float @llvm.fma.f32(float %x, float 7.0, float %mul)
   ret float %fma
 }
 
 ; The FMA is now fully 'fast'. This implies that reassociation is allowed.
 
 ; FMFDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'fmul_fma_fast1:'
-; FMFDEBUG:         fma {{t[0-9]+}}
+; FMFDEBUG:         fma nnan ninf nsz arcp contract afn reassoc  {{t[0-9]+}}
 ; FMFDEBUG:       Type-legalized selection DAG: %bb.0 'fmul_fma_fast1:'
 
 ; GLOBALDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'fmul_fma_fast1:'
 ; GLOBALDEBUG:         fmul reassoc {{t[0-9]+}}
 ; GLOBALDEBUG:       Type-legalized selection DAG: %bb.0 'fmul_fma_fast1:'
 
 define float @fmul_fma_fast1(float %x) {
 ; FMF-LABEL: fmul_fma_fast1:
; GLOBAL-NEXT:    blr
   %mul = fmul float %x, 42.0
   %fma = call fast float @llvm.fma.f32(float %x, float 7.0, float %mul)
   ret float %fma
 }
 
 ; This shouldn't change anything - the intermediate fmul result is now also flagged.
 
 ; FMFDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'fmul_fma_fast2:'
-; FMFDEBUG:         fma {{t[0-9]+}}
+; FMFDEBUG:         fma nnan ninf nsz arcp contract afn reassoc  {{t[0-9]+}}
 ; FMFDEBUG:       Type-legalized selection DAG: %bb.0 'fmul_fma_fast2:'
 
 ; GLOBALDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'fmul_fma_fast2:'
 ; GLOBALDEBUG:         fmul reassoc {{t[0-9]+}}
 ; GLOBALDEBUG:       Type-legalized selection DAG: %bb.0 'fmul_fma_fast2:'
 
 define float @fmul_fma_fast2(float %x) {
 ; FMF-LABEL: fmul_fma_fast2:
; GLOBAL-NEXT:    blr
   %mul = fmul fast float %x, 42.0
   %fma = call fast float @llvm.fma.f32(float %x, float 7.0, float %mul)
   ret float %fma
 }
 
 ; Reduced precision for sqrt is allowed - should use estimate and NR iterations.
 
 ; FMFDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'sqrt_afn:'
-; FMFDEBUG:         fsqrt {{t[0-9]+}}
+; FMFDEBUG:         fsqrt afn {{t[0-9]+}}
 ; FMFDEBUG:       Type-legalized selection DAG: %bb.0 'sqrt_afn:'
 
 ; GLOBALDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'sqrt_afn:'
 ; GLOBALDEBUG:         fmul reassoc {{t[0-9]+}}
 ; GLOBALDEBUG:       Type-legalized selection DAG: %bb.0 'sqrt_afn:'
 
 define float @sqrt_afn(float %x) {
 ; FMF-LABEL: sqrt_afn:

 ; GLOBAL-NEXT:    blr
   %rt = call afn float @llvm.sqrt.f32(float %x)
   ret float %rt
 }
 
 ; The call is now fully 'fast'. This implies that approximation is allowed.
 
 ; FMFDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'sqrt_fast:'
-; FMFDEBUG:         fsqrt {{t[0-9]+}}
+; FMFDEBUG:         fsqrt nnan ninf nsz arcp contract afn reassoc {{t[0-9]+}}
 ; FMFDEBUG:       Type-legalized selection DAG: %bb.0 'sqrt_fast:'
 
 ; GLOBALDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'sqrt_fast:'
 ; GLOBALDEBUG:         fmul reassoc {{t[0-9]+}}
 ; GLOBALDEBUG:       Type-legalized selection DAG: %bb.0 'sqrt_fast:'
 
 define float @sqrt_fast(float %x) {
 ; FMF-LABEL: sqrt_fast:

test/CodeGen/X86/fminnum.ll

; AVX-NEXT:    retq
   ret <8 x double> %z
 }
 
 ; FIXME: The IR-level FMF should propagate to the node. With nnan, there's no need to blend.
 
 define float @minnum_intrinsic_nnan_fmf_f32(float %a, float %b) {
 ; SSE-LABEL: minnum_intrinsic_nnan_fmf_f32:
 ; SSE:       # %bb.0:
-; SSE-NEXT:    movaps %xmm0, %xmm2
-; SSE-NEXT:    cmpunordss %xmm0, %xmm2
-; SSE-NEXT:    movaps %xmm2, %xmm3
-; SSE-NEXT:    andps %xmm1, %xmm3
-; SSE-NEXT:    minss %xmm0, %xmm1
-; SSE-NEXT:    andnps %xmm1, %xmm2
-; SSE-NEXT:    orps %xmm3, %xmm2
-; SSE-NEXT:    movaps %xmm2, %xmm0
+; SSE-NEXT:    minss %xmm1, %xmm0
 ; SSE-NEXT:    retq
 ;
 ; AVX-LABEL: minnum_intrinsic_nnan_fmf_f32:
 ; AVX:       # %bb.0:
-; AVX-NEXT:    vminss %xmm0, %xmm1, %xmm2
-; AVX-NEXT:    vcmpunordss %xmm0, %xmm0, %xmm0
-; AVX-NEXT:    vblendvps %xmm0, %xmm1, %xmm2, %xmm0
+; AVX-NEXT:    vminss %xmm1, %xmm0, %xmm0
 ; AVX-NEXT:    retq
   %r = tail call nnan float @llvm.minnum.f32(float %a, float %b)
   ret float %r
 }
 
 ; FIXME: Make sure vectors work too.
 
 define <2 x double> @minnum_intrinsic_nnan_fmf_v2f64(<2 x double> %a, <2 x double> %b) {