[PATCH] D25998: AMDGPU/SI: Don't use non-0 waitcnt values when waiting on Flat instructions
Tom Stellard via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 26 09:53:31 PDT 2016
tstellarAMD created this revision.
tstellarAMD added reviewers: arsenm, tony-tye.
tstellarAMD added a subscriber: llvm-commits.
Herald added subscribers: yaxunl, nhaehnle, wdng, kzhuravl.
Flat instruction can return out of order, so we need always need to wait
for all the outstanding flat operations.
https://reviews.llvm.org/D25998
Files:
lib/Target/AMDGPU/SIInsertWaits.cpp
test/CodeGen/MIR/AMDGPU/waitcnt.mir
Index: test/CodeGen/MIR/AMDGPU/waitcnt.mir
===================================================================
--- /dev/null
+++ test/CodeGen/MIR/AMDGPU/waitcnt.mir
@@ -0,0 +1,24 @@
+# RUN: llc -march=amdgcn -mcpu=fiji -run-pass si-insert-waits %s -o - | FileCheck %s
+
+--- |
+ define void @flat_zero_waitcnt() { ret void }
+...
+---
+
+# CHECK-LABEL: name: flat_zero_waitcnt
+
+# CHECK-LABEL: bb.0:
+# CHECK: FLAT_LOAD_DWORD
+# CHECK: FLAT_LOAD_DWORDX4
+# s_waitcnt vmcnt(0) lgkmcnt(0)
+# CHECK: S_WAITCNT 112
+
+name: flat_zero_waitcnt
+
+body: |
+ bb.0:
+ %vgpr0 = FLAT_LOAD_DWORD %vgpr1_vgpr2, 0, 0, 0, implicit %exec, implicit %flat_scr
+ %vgpr3_vgpr4_vgpr5_vgpr6 = FLAT_LOAD_DWORDX4 %vgpr7_vgpr8, 0, 0, 0, implicit %exec, implicit %flat_scr
+ %vgpr0 = V_MOV_B32_e32 %vgpr1, implicit %exec
+ S_ENDPGM
+...
Index: lib/Target/AMDGPU/SIInsertWaits.cpp
===================================================================
--- lib/Target/AMDGPU/SIInsertWaits.cpp
+++ lib/Target/AMDGPU/SIInsertWaits.cpp
@@ -93,6 +93,9 @@
bool LastInstWritesM0;
+ /// Whether or not we have flat operations outstanding.
+ bool IsFlatOutstanding;
+
/// \brief Whether the machine function returns void
bool ReturnsVoid;
@@ -294,6 +297,9 @@
Counters Limit = ZeroCounts;
unsigned Sum = 0;
+ if (TII->isFLAT(*I))
+ IsFlatOutstanding = true;
+
for (unsigned i = 0; i < 3; ++i) {
LastIssued.Array[i] += Increment.Array[i];
if (Increment.Array[i])
@@ -368,8 +374,9 @@
// Figure out if the async instructions execute in order
bool Ordered[3];
- // VM_CNT is always ordered
- Ordered[0] = true;
+ // VM_CNT is always ordered except when there are flat instructions, which
+ // can return out of order.
+ Ordered[0] = !IsFlatOutstanding;
// EXP_CNT is unordered if we have both EXP & VM-writes
Ordered[1] = ExpInstrTypesSeen == 3;
@@ -419,6 +426,7 @@
LastOpcodeType = OTHER;
LastInstWritesM0 = false;
+ IsFlatOutstanding = true;
return true;
}
@@ -532,6 +540,7 @@
LastIssued = ZeroCounts;
LastOpcodeType = OTHER;
LastInstWritesM0 = false;
+ IsFlatOutstanding = false;
ReturnsVoid = MF.getInfo<SIMachineFunctionInfo>()->returnsVoid();
memset(&UsedRegs, 0, sizeof(UsedRegs));
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