[PATCH] R600: Use legacy (0 * anything = 0) MUL instructions for pow intrinsics

[Michel Dänzer]

From: Michel Dänzer <michel.daenzer at amd.com>

Fixes wrong lighting in some corner cases with r600g and radeonsi, e.g.
manifested by failure of two piglit/glean tests and intermittent black
patches in many apps.

Tested on SI and RS880.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=62012 [radeonsi]
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=58150 [r600g]

NOTE: This is a candidate for the Mesa stable branch.

Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
---
 lib/Target/R600/R600ISelLowering.cpp | 11 -----------
 lib/Target/R600/R600ISelLowering.h   |  1 -
 lib/Target/R600/R600Instructions.td  |  5 ++++-
 lib/Target/R600/SIInstructions.td    |  3 +--
 4 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/lib/Target/R600/R600ISelLowering.cpp b/lib/Target/R600/R600ISelLowering.cpp
index a73691d..7bdba83 100644
--- a/lib/Target/R600/R600ISelLowering.cpp
+++ b/lib/Target/R600/R600ISelLowering.cpp
@@ -58,7 +58,6 @@ R600TargetLowering::R600TargetLowering(TargetMachine &TM) :
   setOperationAction(ISD::INTRINSIC_VOID, MVT::Other, Custom);
   setOperationAction(ISD::INTRINSIC_WO_CHAIN, MVT::Other, Custom);
   setOperationAction(ISD::INTRINSIC_WO_CHAIN, MVT::i1, Custom);
-  setOperationAction(ISD::FPOW, MVT::f32, Custom);
 
   setOperationAction(ISD::ROTL, MVT::i32, Custom);
 
@@ -316,7 +315,6 @@ SDValue R600TargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const
   case ISD::SELECT: return LowerSELECT(Op, DAG);
   case ISD::STORE: return LowerSTORE(Op, DAG);
   case ISD::LOAD: return LowerLOAD(Op, DAG);
-  case ISD::FPOW: return LowerFPOW(Op, DAG);
   case ISD::FrameIndex: return LowerFrameIndex(Op, DAG);
   case ISD::INTRINSIC_VOID: {
     SDValue Chain = Op.getOperand(0);
@@ -918,15 +916,6 @@ SDValue R600TargetLowering::LowerLOAD(SDValue Op, SelectionDAG &DAG) const
   return DAG.getMergeValues(Ops, 2, DL);
 }
 
-SDValue R600TargetLowering::LowerFPOW(SDValue Op,
-    SelectionDAG &DAG) const {
-  DebugLoc DL = Op.getDebugLoc();
-  EVT VT = Op.getValueType();
-  SDValue LogBase = DAG.getNode(ISD::FLOG2, DL, VT, Op.getOperand(0));
-  SDValue MulLogBase = DAG.getNode(ISD::FMUL, DL, VT, Op.getOperand(1), LogBase);
-  return DAG.getNode(ISD::FEXP2, DL, VT, MulLogBase);
-}
-
 /// XXX Only kernel functions are supported, so we can assume for now that
 /// every function is a kernel function, but in the future we should use
 /// separate calling conventions for kernel and non-kernel functions.
diff --git a/lib/Target/R600/R600ISelLowering.h b/lib/Target/R600/R600ISelLowering.h
index 5cb4b91..2c09acb 100644
--- a/lib/Target/R600/R600ISelLowering.h
+++ b/lib/Target/R600/R600ISelLowering.h
@@ -59,7 +59,6 @@ private:
   SDValue LowerSELECT(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerSTORE(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerFPTOUINT(SDValue Op, SelectionDAG &DAG) const;
-  SDValue LowerFPOW(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerLOAD(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerFrameIndex(SDValue Op, SelectionDAG &DAG) const;
 
diff --git a/lib/Target/R600/R600Instructions.td b/lib/Target/R600/R600Instructions.td
index 8c50d54..a6daadf 100644
--- a/lib/Target/R600/R600Instructions.td
+++ b/lib/Target/R600/R600Instructions.td
@@ -1141,6 +1141,7 @@ let Predicates = [isR600] in {
   def RECIP_UINT_r600 : RECIP_UINT_Common <0x78>;
 
   defm DIV_r600 : DIV_Common<RECIP_IEEE_r600>;
+  def : POW_Common <LOG_IEEE_r600, EXP_IEEE_r600, MUL, R600_Reg32>;
   def TGSI_LIT_Z_r600 : TGSI_LIT_Z_Common<MUL_LIT_r600, LOG_CLAMPED_r600, EXP_IEEE_r600>;
 
   def : Pat<(fsqrt R600_Reg32:$src),
@@ -1212,6 +1213,7 @@ def RECIPSQRT_IEEE_eg : RECIPSQRT_IEEE_Common<0x89>;
 def SIN_eg : SIN_Common<0x8D>;
 def COS_eg : COS_Common<0x8E>;
 
+def : POW_Common <LOG_IEEE_eg, EXP_IEEE_eg, MUL, R600_Reg32>;
 def : SIN_PAT <SIN_eg>;
 def : COS_PAT <COS_eg>;
 def : Pat<(fsqrt R600_Reg32:$src),
@@ -1540,13 +1542,14 @@ def MULLO_UINT_cm : MULLO_UINT_Common<0x91>;
 def MULHI_UINT_cm : MULHI_UINT_Common<0x92>;
 def RECIPSQRT_CLAMPED_cm : RECIPSQRT_CLAMPED_Common<0x87>;
 def EXP_IEEE_cm : EXP_IEEE_Common<0x81>;
-def LOG_IEEE_ : LOG_IEEE_Common<0x83>;
+def LOG_IEEE_cm : LOG_IEEE_Common<0x83>;
 def RECIP_CLAMPED_cm : RECIP_CLAMPED_Common<0x84>;
 def RECIPSQRT_IEEE_cm : RECIPSQRT_IEEE_Common<0x89>;
 def SIN_cm : SIN_Common<0x8D>;
 def COS_cm : COS_Common<0x8E>;
 } // End isVector = 1
 
+def : POW_Common <LOG_IEEE_cm, EXP_IEEE_cm, MUL, R600_Reg32>;
 def : SIN_PAT <SIN_cm>;
 def : COS_PAT <COS_cm>;
 
diff --git a/lib/Target/R600/SIInstructions.td b/lib/Target/R600/SIInstructions.td
index 05b04a9..dc75f01 100644
--- a/lib/Target/R600/SIInstructions.td
+++ b/lib/Target/R600/SIInstructions.td
@@ -1442,8 +1442,7 @@ def : Pat <
 /********** ================== **********/
 
 /* llvm.AMDGPU.pow */
-/* XXX: We are using IEEE MUL, not the 0 * anything = 0 MUL, is this correct? */
-def : POW_Common <V_LOG_F32_e32, V_EXP_F32_e32, V_MUL_F32_e32, VReg_32>;
+def : POW_Common <V_LOG_F32_e32, V_EXP_F32_e32, V_MUL_LEGACY_F32_e32, VReg_32>;
 
 def : Pat <
   (int_AMDGPU_div VSrc_32:$src0, VSrc_32:$src1),
-- 
1.8.2.rc3