[llvm] r225405 - R600/SI: Only fold immediates that have one use

[Tom Stellard]

Author: tstellar
Date: Wed Jan  7 16:18:27 2015
New Revision: 225405

URL: http://llvm.org/viewvc/llvm-project?rev=225405&view=rev
Log:
R600/SI: Only fold immediates that have one use

Folding the same immediate into multiple instruction will increase
program size, which can hurt performance.

Modified:
    llvm/trunk/lib/Target/R600/SIFoldOperands.cpp
    llvm/trunk/test/CodeGen/R600/operand-folding.ll

Modified: llvm/trunk/lib/Target/R600/SIFoldOperands.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/R600/SIFoldOperands.cpp?rev=225405&r1=225404&r2=225405&view=diff
==============================================================================
--- llvm/trunk/lib/Target/R600/SIFoldOperands.cpp (original)
+++ llvm/trunk/lib/Target/R600/SIFoldOperands.cpp Wed Jan  7 16:18:27 2015
@@ -138,6 +138,14 @@ bool SIFoldOperands::runOnMachineFunctio
         continue;
 
       MachineOperand &OpToFold = MI.getOperand(1);
+      bool FoldingImm = OpToFold.isImm() || OpToFold.isFPImm();
+
+      // Folding immediates with more than one use will increase program side.
+      // FIXME: This will also reduce register usage, which may be better
+      // in some cases.  A better heuristic is needed.
+      if (FoldingImm && !TII->isInlineConstant(OpToFold) &&
+          !MRI.hasOneUse(MI.getOperand(0).getReg()))
+        continue;
 
       // FIXME: Fold operands with subregs.
       if (OpToFold.isReg() &&
@@ -158,7 +166,6 @@ bool SIFoldOperands::runOnMachineFunctio
           continue;
         }
 
-        bool FoldingImm = OpToFold.isImm() || OpToFold.isFPImm();
         APInt Imm;
 
         if (FoldingImm) {

Modified: llvm/trunk/test/CodeGen/R600/operand-folding.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/R600/operand-folding.ll?rev=225405&r1=225404&r2=225405&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/R600/operand-folding.ll (original)
+++ llvm/trunk/test/CodeGen/R600/operand-folding.ll Wed Jan  7 16:18:27 2015
@@ -53,5 +53,40 @@ entry:
   ret void
 }
 
+; Inline constants should always be folded.
+
+; CHECK-LABEL: {{^}}vector_inline:
+; CHECK: v_xor_b32_e32 v{{[0-9]+}}, 5, v{{[0-9]+}}
+; CHECK: v_xor_b32_e32 v{{[0-9]+}}, 5, v{{[0-9]+}}
+; CHECK: v_xor_b32_e32 v{{[0-9]+}}, 5, v{{[0-9]+}}
+; CHECK: v_xor_b32_e32 v{{[0-9]+}}, 5, v{{[0-9]+}}
+
+define void @vector_inline(<4 x i32> addrspace(1)* %out) {
+entry:
+  %tmp0 = call i32 @llvm.r600.read.tidig.x()
+  %tmp1 = add i32 %tmp0, 1
+  %tmp2 = add i32 %tmp0, 2
+  %tmp3 = add i32 %tmp0, 3
+  %vec0 = insertelement <4 x i32> undef, i32 %tmp0, i32 0
+  %vec1 = insertelement <4 x i32> %vec0, i32 %tmp1, i32 1
+  %vec2 = insertelement <4 x i32> %vec1, i32 %tmp2, i32 2
+  %vec3 = insertelement <4 x i32> %vec2, i32 %tmp3, i32 3
+  %tmp4 = xor <4 x i32> <i32 5, i32 5, i32 5, i32 5>, %vec3
+  store <4 x i32> %tmp4, <4 x i32> addrspace(1)* %out
+  ret void
+}
+
+; Immediates with one use should be folded
+; CHECK-LABEL: {{^}}imm_one_use:
+; CHECK: v_xor_b32_e32 v{{[0-9]+}}, 0x64, v{{[0-9]+}}
+
+define void @imm_one_use(i32 addrspace(1)* %out) {
+entry:
+  %tmp0 = call i32 @llvm.r600.read.tidig.x()
+  %tmp1 = xor i32 %tmp0, 100
+  store i32 %tmp1, i32 addrspace(1)* %out
+  ret void
+}
+
 declare i32 @llvm.r600.read.tidig.x() #0
 attributes #0 = { readnone }