[MBP] Move a latch block with conditional exit and multi predecessors to top of loop

Current findBestLoopTop can find and move one kind of block to top, a latch block has one successor. Another common case is:

    * a latch block
    * it has two successors, one is loop header, another is exit
    * it has more than one predecessors

If it is below one of its predecessors P, only P can fall through to it, all other predecessors need a jump to it, and another conditional jump to loop header. If it is moved before loop header, all its predecessors jump to it, then fall through to loop header. So all its predecessors except P can reduce one taken branch.

Differential Revision: https://reviews.llvm.org/D43256

llvm-svn: 363471

1 files changed, 4 insertions, 4 deletions

diff --git a/llvm/test/CodeGen/AMDGPU/optimize-negated-cond.ll b/llvm/test/CodeGen/AMDGPU/optimize-negated-cond.ll
index be5d8d47205..2be99267c4e 100644
--- a/llvm/test/CodeGen/AMDGPU/optimize-negated-cond.ll
+++ b/llvm/test/CodeGen/AMDGPU/optimize-negated-cond.ll
@@ -3,11 +3,11 @@
 ; GCN-LABEL: {{^}}negated_cond:
 ; GCN: BB0_1:
 ; GCN:   v_cmp_eq_u32_e64 [[CC:[^,]+]],
-; GCN: BB0_2:
+; GCN: BB0_3:
 ; GCN-NOT: v_cndmask_b32
 ; GCN-NOT: v_cmp
 ; GCN:   s_andn2_b64 vcc, exec, [[CC]]
-; GCN:   s_cbranch_vccnz BB0_4
+; GCN:   s_cbranch_vccnz BB0_2
 define amdgpu_kernel void @negated_cond(i32 addrspace(1)* %arg1) {
 bb:
   br label %bb1
@@ -36,11 +36,11 @@ bb4:
 
 ; GCN-LABEL: {{^}}negated_cond_dominated_blocks:
 ; GCN:   v_cmp_eq_u32_e64 [[CC:[^,]+]],
-; GCN: BB1_1:
+; GCN: %bb4
 ; GCN-NOT: v_cndmask_b32
 ; GCN-NOT: v_cmp
 ; GCN:   s_andn2_b64 vcc, exec, [[CC]]
-; GCN:   s_cbranch_vccz BB1_3
+; GCN:   s_cbranch_vccnz BB1_1
 define amdgpu_kernel void @negated_cond_dominated_blocks(i32 addrspace(1)* %arg1) {
 bb:
   br label %bb2