[llvm] 7ba61ea - [AMDGPU] More precise limit on SALU cycles in s_delay_alu instructions

[Jay Foad via llvm-commits]

Author: Jay Foad
Date: 2023-03-05T08:14:15Z
New Revision: 7ba61eaf34c34f1bec6bfa920f3cfa5e5174eb71

URL: https://github.com/llvm/llvm-project/commit/7ba61eaf34c34f1bec6bfa920f3cfa5e5174eb71
DIFF: https://github.com/llvm/llvm-project/commit/7ba61eaf34c34f1bec6bfa920f3cfa5e5174eb71.diff

LOG: [AMDGPU] More precise limit on SALU cycles in s_delay_alu instructions

This just tweaks the fix for D145232 to make the limit more precise, so
that we could actually emit a delay of 3 SALU cycles (the maximum) if we
had any SALU instructions that required it.

Added: 
    

Modified: 
    llvm/lib/Target/AMDGPU/AMDGPUInsertDelayAlu.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/AMDGPU/AMDGPUInsertDelayAlu.cpp b/llvm/lib/Target/AMDGPU/AMDGPUInsertDelayAlu.cpp
index 57d0fdacf7cf7..a3a13062a1e11 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUInsertDelayAlu.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUInsertDelayAlu.cpp
@@ -83,9 +83,9 @@ class AMDGPUInsertDelayAlu : public MachineFunctionPass {
     // an s_delay_alu instruction.
     static constexpr unsigned TRANS_MAX = 4;
 
-    // The maximum number of SALU cycles we can encode in an s_delay_alu
-    // instruction.
-    static constexpr unsigned SALU_CYCLES_MAX = 3;
+    // One larger than the maximum number of SALU cycles we can encode in an
+    // s_delay_alu instruction.
+    static constexpr unsigned SALU_CYCLES_MAX = 4;
 
     // If it was written by a (non-TRANS) VALU, remember how many clock cycles
     // are left until it completes, and how many other (non-TRANS) VALU we have
@@ -284,6 +284,7 @@ class AMDGPUInsertDelayAlu : public MachineFunctionPass {
 
     // Wait for an SALU instruction.
     if (Delay.SALUCycles) {
+      assert(Delay.SALUCycles < DelayInfo::SALU_CYCLES_MAX);
       if (Imm & 0x780) {
         // We have already encoded a VALU and a TRANS delay. There's no room in
         // the encoding for an SALU delay as well, so just drop it.