AMDGPU/SI: Fix a mis-compilation of multi-level breaks

Summary:
Under certain circumstances, multi-level breaks (or what is understood by
the control flow passes as such) could be miscompiled in a way that causes
infinite loops, by emitting incorrect control flow intrinsics.

This fixes a hang in
dEQP-GLES3.functional.shaders.loops.while_dynamic_iterations.conditional_continue_vertex

Reviewers: arsenm, tstellarAMD

Subscribers: arsenm, llvm-commits

Differential Revision: http://reviews.llvm.org/D18967

llvm-svn: 266088

1 files changed, 41 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/AMDGPU/multilevel-break.ll b/llvm/test/CodeGen/AMDGPU/multilevel-break.ll
new file mode 100644
index 00000000000..e1130c9125e
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/multilevel-break.ll
@@ -0,0 +1,41 @@
+; RUN: opt -S -mtriple=amdgcn-- -structurizecfg -si-annotate-control-flow < %s | FileCheck %s
+
+; CHECK-LABEL: {{^}}define amdgpu_vs void @main
+; CHECK: main_body:
+; CHECK: LOOP.outer:
+; CHECK: LOOP:
+; CHECK:     [[if:%[0-9]+]] = call { i1, i64 } @llvm.amdgcn.if(
+; CHECK:     [[if_exec:%[0-9]+]] = extractvalue { i1, i64 } [[if]], 1
+;
+; CHECK: Flow:
+;
+; Ensure two else.break calls, for both the inner and outer loops
+;
+; CHECK:        call i64 @llvm.amdgcn.else.break(i64 [[if_exec]],
+; CHECK-NEXT:   call i64 @llvm.amdgcn.else.break(i64 [[if_exec]],
+; CHECK-NEXT:   call void @llvm.amdgcn.end.cf
+;
+; CHECK: Flow1:
+define amdgpu_vs void @main(<4 x float> %vec, i32 %ub, i32 %cont) {
+main_body:
+  br label %LOOP.outer
+
+LOOP.outer:                                       ; preds = %ENDIF, %main_body
+  %tmp43 = phi i32 [ 0, %main_body ], [ %tmp47, %ENDIF ]
+  br label %LOOP
+
+LOOP:                                             ; preds = %ENDIF, %LOOP.outer
+  %tmp45 = phi i32 [ %tmp43, %LOOP.outer ], [ %tmp47, %ENDIF ]
+  %tmp47 = add i32 %tmp45, 1
+  %tmp48 = icmp slt i32 %tmp45, %ub
+  br i1 %tmp48, label %ENDIF, label %IF
+
+IF:                                               ; preds = %LOOP
+  ret void
+
+ENDIF:                                            ; preds = %LOOP
+  %tmp51 = icmp eq i32 %tmp47, %cont
+  br i1 %tmp51, label %LOOP, label %LOOP.outer
+}
+
+attributes #0 = { nounwind readnone }