[llvm] r309832 - AMDGPU: Restore using MRI to find highest used regs

[Matt Arsenault via llvm-commits]

Author: arsenm
Date: Wed Aug  2 10:15:01 2017
New Revision: 309832

URL: http://llvm.org/viewvc/llvm-project?rev=309832&view=rev
Log:
AMDGPU: Restore using MRI to find highest used regs

If there are no calls, this is a faster path than
searching the entire program for calls.

This was supposed to be left in r309781.
Fixes unused variable warning.

Modified:
    llvm/trunk/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp

Modified: llvm/trunk/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp?rev=309832&r1=309831&r2=309832&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp (original)
+++ llvm/trunk/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp Wed Aug  2 10:15:01 2017
@@ -500,13 +500,31 @@ AMDGPUAsmPrinter::SIFunctionResourceInfo
 
   // If there are no calls, MachineRegisterInfo can tell us the used register
   // count easily.
+  if (!FrameInfo.hasCalls()) {
+    MCPhysReg HighestVGPRReg = AMDGPU::NoRegister;
+    for (MCPhysReg Reg : reverse(AMDGPU::VGPR_32RegClass.getRegisters())) {
+      if (MRI.isPhysRegUsed(Reg)) {
+        HighestVGPRReg = Reg;
+        break;
+      }
+    }
 
-  MCPhysReg HighestVGPRReg = AMDGPU::NoRegister;
-  for (MCPhysReg Reg : reverse(AMDGPU::VGPR_32RegClass.getRegisters())) {
-    if (MRI.isPhysRegUsed(Reg)) {
-      HighestVGPRReg = Reg;
-      break;
+    MCPhysReg HighestSGPRReg = AMDGPU::NoRegister;
+    for (MCPhysReg Reg : reverse(AMDGPU::SGPR_32RegClass.getRegisters())) {
+      if (MRI.isPhysRegUsed(Reg)) {
+        HighestSGPRReg = Reg;
+        break;
+      }
     }
+
+    // We found the maximum register index. They start at 0, so add one to get the
+    // number of registers.
+    Info.NumVGPR = HighestVGPRReg == AMDGPU::NoRegister ? 0 :
+      TRI.getHWRegIndex(HighestVGPRReg) + 1;
+    Info.NumExplicitSGPR = HighestSGPRReg == AMDGPU::NoRegister ? 0 :
+      TRI.getHWRegIndex(HighestSGPRReg) + 1;
+
+    return Info;
   }
 
   int32_t MaxVGPR = -1;