CodeGen: Allow small copyable blocks to "break" the CFG.

When choosing the best successor for a block, ordinarily we would have preferred
a block that preserves the CFG unless there is a strong probability the other
direction. For small blocks that can be duplicated we now skip that requirement
as well, subject to some simple frequency calculations.

Differential Revision: https://reviews.llvm.org/D28583

llvm-svn: 293716

4 files changed, 29 insertions, 24 deletions

diff --git a/llvm/test/CodeGen/ARM/arm-and-tst-peephole.ll b/llvm/test/CodeGen/ARM/arm-and-tst-peephole.ll
index 9bd2077e4d0..2fb0d231825 100644
--- a/llvm/test/CodeGen/ARM/arm-and-tst-peephole.ll
+++ b/llvm/test/CodeGen/ARM/arm-and-tst-peephole.ll
@@ -49,9 +49,9 @@ tailrecurse.switch:                               ; preds = %tailrecurse
 ; V8-NEXT: beq
 ; V8-NEXT: %tailrecurse.switch
 ; V8: cmp
-; V8-NEXT: bne
-; V8-NEXT: b	
-; The trailing space in the last line checks that the branch is unconditional
+; V8-NEXT: beq
+; V8-NEXT: %sw.epilog
+; V8-NEXT: bx lr
   switch i32 %and, label %sw.epilog [
     i32 1, label %sw.bb
     i32 3, label %sw.bb6
diff --git a/llvm/test/CodeGen/ARM/atomic-op.ll b/llvm/test/CodeGen/ARM/atomic-op.ll
index e6a4949d53c..23c4ccea460 100644
--- a/llvm/test/CodeGen/ARM/atomic-op.ll
+++ b/llvm/test/CodeGen/ARM/atomic-op.ll
@@ -320,10 +320,10 @@ define i32 @test_cmpxchg_fail_order1(i32 *%addr, i32 %desired, i32 %new) {
 ; CHECK:     strex   [[SUCCESS:r[0-9]+]], r2, [r[[ADDR]]]
 ; CHECK:     cmp     [[SUCCESS]], #0
 ; CHECK:     bne     [[LOOP_BB]]
-; CHECK:     b       [[END_BB:\.?LBB[0-9]+_[0-9]+]]
+; CHECK:     dmb     ish
+; CHECK:     bx      lr
 ; CHECK: [[FAIL_BB]]:
 ; CHECK-NEXT: clrex
-; CHECK-NEXT: [[END_BB]]:
 ; CHECK:     dmb     ish
 ; CHECK:     bx      lr
 
diff --git a/llvm/test/CodeGen/ARM/atomic-ops-v8.ll b/llvm/test/CodeGen/ARM/atomic-ops-v8.ll
index 77b850bd617..d1575ed12e4 100644
--- a/llvm/test/CodeGen/ARM/atomic-ops-v8.ll
+++ b/llvm/test/CodeGen/ARM/atomic-ops-v8.ll
@@ -1045,20 +1045,21 @@ define i8 @test_atomic_cmpxchg_i8(i8 zeroext %wanted, i8 zeroext %new) nounwind
   ;  function there.
 ; CHECK-ARM-NEXT:   cmp r[[OLD]], r0
 ; CHECK-THUMB-NEXT: cmp r[[OLD]], r[[WANTED]]
-; CHECK-NEXT: bne .LBB{{[0-9]+}}_3
+; CHECK-NEXT: bne .LBB{{[0-9]+}}_4
 ; CHECK-NEXT: BB#2:
   ; As above, r1 is a reasonable guess.
 ; CHECK: strexb [[STATUS:r[0-9]+]], r1, [r[[ADDR]]]
 ; CHECK-NEXT: cmp [[STATUS]], #0
 ; CHECK-NEXT: bne .LBB{{[0-9]+}}_1
-; CHECK-NEXT: b .LBB{{[0-9]+}}_4
-; CHECK-NEXT: .LBB{{[0-9]+}}_3:
-; CHECK-NEXT: clrex
+; CHECK-ARM: mov r0, r[[OLD]]
+; CHECK: bx lr
 ; CHECK-NEXT: .LBB{{[0-9]+}}_4:
+; CHECK-NEXT: clrex
 ; CHECK-NOT: dmb
 ; CHECK-NOT: mcr
 
 ; CHECK-ARM: mov r0, r[[OLD]]
+; CHECK-ARM-NEXT: bx lr
    ret i8 %old
 }
 
@@ -1078,20 +1079,21 @@ define i16 @test_atomic_cmpxchg_i16(i16 zeroext %wanted, i16 zeroext %new) nounw
   ;  function there.
 ; CHECK-ARM-NEXT:   cmp r[[OLD]], r0
 ; CHECK-THUMB-NEXT: cmp r[[OLD]], r[[WANTED]]
-; CHECK-NEXT: bne .LBB{{[0-9]+}}_3
+; CHECK-NEXT: bne .LBB{{[0-9]+}}_4
 ; CHECK-NEXT: BB#2:
   ; As above, r1 is a reasonable guess.
 ; CHECK: stlexh [[STATUS:r[0-9]+]], r1, [r[[ADDR]]]
 ; CHECK-NEXT: cmp [[STATUS]], #0
 ; CHECK-NEXT: bne .LBB{{[0-9]+}}_1
-; CHECK-NEXT: b .LBB{{[0-9]+}}_4
-; CHECK-NEXT: .LBB{{[0-9]+}}_3:
-; CHECK-NEXT: clrex
+; CHECK-ARM: mov r0, r[[OLD]]
+; CHECK: bx lr
 ; CHECK-NEXT: .LBB{{[0-9]+}}_4:
+; CHECK-NEXT: clrex
 ; CHECK-NOT: dmb
 ; CHECK-NOT: mcr
 
 ; CHECK-ARM: mov r0, r[[OLD]]
+; CHECK-ARM-NEXT: bx lr
    ret i16 %old
 }
 
@@ -1110,20 +1112,21 @@ define void @test_atomic_cmpxchg_i32(i32 %wanted, i32 %new) nounwind {
   ; r0 below is a reasonable guess but could change: it certainly comes into the
   ;  function there.
 ; CHECK-NEXT: cmp r[[OLD]], r0
-; CHECK-NEXT: bne .LBB{{[0-9]+}}_3
+; CHECK-NEXT: bne .LBB{{[0-9]+}}_4
 ; CHECK-NEXT: BB#2:
   ; As above, r1 is a reasonable guess.
 ; CHECK: stlex [[STATUS:r[0-9]+]], r1, [r[[ADDR]]]
 ; CHECK-NEXT: cmp [[STATUS]], #0
 ; CHECK-NEXT: bne .LBB{{[0-9]+}}_1
-; CHECK-NEXT: b .LBB{{[0-9]+}}_4
-; CHECK-NEXT: .LBB{{[0-9]+}}_3:
-; CHECK-NEXT: clrex
+; CHECK: str{{(.w)?}} r[[OLD]],
+; CHECK-NEXT: bx lr
 ; CHECK-NEXT: .LBB{{[0-9]+}}_4:
+; CHECK-NEXT: clrex
 ; CHECK-NOT: dmb
 ; CHECK-NOT: mcr
 
 ; CHECK: str{{(.w)?}} r[[OLD]],
+; CHECK-ARM-NEXT: bx lr
    ret void
 }
 
@@ -1148,16 +1151,16 @@ define void @test_atomic_cmpxchg_i64(i64 %wanted, i64 %new) nounwind {
 ; CHECK-BE-DAG: eor{{(\.w)?}} [[MISMATCH_LO:r[0-9]+|lr]], [[OLD1]], r0
 ; CHECK-ARM-BE: orrs{{(\.w)?}} {{r[0-9]+}}, [[MISMATCH_HI]], [[MISMATCH_LO]]
 ; CHECK-THUMB-BE: orrs{{(\.w)?}} {{(r[0-9]+, )?}}[[MISMATCH_LO]], [[MISMATCH_HI]]
-; CHECK-NEXT: bne .LBB{{[0-9]+}}_3
+; CHECK-NEXT: bne .LBB{{[0-9]+}}_4
 ; CHECK-NEXT: BB#2:
   ; As above, r2, r3 is a reasonable guess.
 ; CHECK: strexd [[STATUS:r[0-9]+]], r2, r3, [r[[ADDR]]]
 ; CHECK-NEXT: cmp [[STATUS]], #0
 ; CHECK-NEXT: bne .LBB{{[0-9]+}}_1
-; CHECK-NEXT: b .LBB{{[0-9]+}}_4
-; CHECK-NEXT: .LBB{{[0-9]+}}_3:
-; CHECK-NEXT: clrex
+; CHECK: strd [[OLD1]], [[OLD2]], [r[[ADDR]]]
+; CHECK-NEXT: pop
 ; CHECK-NEXT: .LBB{{[0-9]+}}_4:
+; CHECK-NEXT: clrex
 ; CHECK-NOT: dmb
 ; CHECK-NOT: mcr
 
diff --git a/llvm/test/CodeGen/ARM/cmpxchg-weak.ll b/llvm/test/CodeGen/ARM/cmpxchg-weak.ll
index 4038528c91b..0d5681aafbc 100644
--- a/llvm/test/CodeGen/ARM/cmpxchg-weak.ll
+++ b/llvm/test/CodeGen/ARM/cmpxchg-weak.ll
@@ -13,14 +13,16 @@ define void @test_cmpxchg_weak(i32 *%addr, i32 %desired, i32 %new) {
 ; CHECK-NEXT:     dmb ish
 ; CHECK-NEXT:     strex   [[SUCCESS:r[0-9]+]], r2, [r0]
 ; CHECK-NEXT:     cmp     [[SUCCESS]], #0
-; CHECK-NEXT:     bne     [[FAILBB:LBB[0-9]+_[0-9]+]]
+; CHECK-NEXT:     beq     [[SUCCESSBB:LBB[0-9]+_[0-9]+]]
 ; CHECK-NEXT: BB#2:
-; CHECK-NEXT:     dmb     ish
 ; CHECK-NEXT:     str     r3, [r0]
 ; CHECK-NEXT:     bx      lr
 ; CHECK-NEXT: [[LDFAILBB]]:
 ; CHECK-NEXT:     clrex
-; CHECK-NEXT: [[FAILBB]]:
+; CHECK-NEXT:     str     r3, [r0]
+; CHECK-NEXT:     bx      lr
+; CHECK-NEXT: [[SUCCESSBB]]:
+; CHECK-NEXT:     dmb     ish
 ; CHECK-NEXT:     str     r3, [r0]
 ; CHECK-NEXT:     bx      lr