R600: Recommit 199842: Add work-around for the CF stack entry HW bug
The unit test is now disabled on non-asserts builds.
The CF stack can be corrupted if you use CF_ALU_PUSH_BEFORE,
CF_ALU_ELSE_AFTER, CF_ALU_BREAK, or CF_ALU_CONTINUE when the number of
sub-entries on the stack is greater than or equal to the stack entry
size and sub-entries modulo 4 is either 0 or 3 (on cedar the bug is
present when number of sub-entries module 8 is either 7 or 0)
We choose to be conservative and always apply the work-around when the
number of sub-enries is greater than or equal to the stack entry size,
so that we can safely over-allocate the stack when we are unsure of the
stack allocation rules.
reviewed-by: Vincent Lejeune <vljn at ovi.com>
llvm-svn: 199905
diff --git a/llvm/lib/Target/R600/R600ControlFlowFinalizer.cpp b/llvm/lib/Target/R600/R600ControlFlowFinalizer.cpp
index 6b42a7a..470ff2e 100644
--- a/llvm/lib/Target/R600/R600ControlFlowFinalizer.cpp
+++ b/llvm/lib/Target/R600/R600ControlFlowFinalizer.cpp
@@ -73,6 +73,44 @@
return false;
}
+bool CFStack::requiresWorkAroundForInst(unsigned Opcode) {
+ if (Opcode == AMDGPU::CF_ALU_PUSH_BEFORE && ST.hasCaymanISA() &&
+ getLoopDepth() > 1)
+ return true;
+
+ if (!ST.hasCFAluBug())
+ return false;
+
+ switch(Opcode) {
+ default: return false;
+ case AMDGPU::CF_ALU_PUSH_BEFORE:
+ case AMDGPU::CF_ALU_ELSE_AFTER:
+ case AMDGPU::CF_ALU_BREAK:
+ case AMDGPU::CF_ALU_CONTINUE:
+ if (CurrentSubEntries == 0)
+ return false;
+ if (ST.getWavefrontSize() == 64) {
+ // We are being conservative here. We only require this work-around if
+ // CurrentSubEntries > 3 &&
+ // (CurrentSubEntries % 4 == 3 || CurrentSubEntries % 4 == 0)
+ //
+ // We have to be conservative, because we don't know for certain that
+ // our stack allocation algorithm for Evergreen/NI is correct. Applying this
+ // work-around when CurrentSubEntries > 3 allows us to over-allocate stack
+ // resources without any problems.
+ return CurrentSubEntries > 3;
+ } else {
+ assert(ST.getWavefrontSize() == 32);
+ // We are being conservative here. We only require the work-around if
+ // CurrentSubEntries > 7 &&
+ // (CurrentSubEntries % 8 == 7 || CurrentSubEntries % 8 == 0)
+ // See the comment on the wavefront size == 64 case for why we are
+ // being conservative.
+ return CurrentSubEntries > 7;
+ }
+ }
+}
+
unsigned CFStack::getSubEntrySize(CFStack::StackItem Item) {
switch(Item) {
default:
@@ -472,9 +510,12 @@
if (MI->getOpcode() == AMDGPU::CF_ALU)
LastAlu.back() = MI;
I++;
+ bool RequiresWorkAround =
+ CFStack.requiresWorkAroundForInst(MI->getOpcode());
switch (MI->getOpcode()) {
case AMDGPU::CF_ALU_PUSH_BEFORE:
- if (ST.hasCaymanISA() && CFStack.getLoopDepth() > 1) {
+ if (RequiresWorkAround) {
+ DEBUG(dbgs() << "Applying bug work-around for ALU_PUSH_BEFORE\n");
BuildMI(MBB, MI, MBB.findDebugLoc(MI), TII->get(AMDGPU::CF_PUSH_EG))
.addImm(CfCount + 1)
.addImm(1);