Enable machine sinking critical edge splitting. e.g.

define double @foo(double %x, double %y, i1 %c) nounwind {
  %a = fdiv double %x, 3.2
  %z = select i1 %c, double %a, double %y
  ret double %z
}

Was:
_foo:
        divsd   LCPI0_0(%rip), %xmm0
        testb   $1, %dil
        jne     LBB0_2
        movaps  %xmm1, %xmm0
LBB0_2:
        ret

Now:
_foo:
        testb   $1, %dil
        je      LBB0_2
        divsd   LCPI0_0(%rip), %xmm0
        ret
LBB0_2:
        movaps  %xmm1, %xmm0
        ret

This avoids the divsd when early exit is taken.
rdar://8454886

llvm-svn: 114372

llvm/lib/CodeGen/MachineSink.cpp

@@ -35,10 +35,7 @@ using namespace llvm;
 static cl::opt<bool> 
 SplitEdges("machine-sink-split",
            cl::desc("Split critical edges during machine sinking"),
-           cl::init(false), cl::Hidden);
+           cl::init(true), cl::Hidden);
-static cl::opt<unsigned>
-SplitLimit("split-limit",
-           cl::init(~0u), cl::Hidden);
 
 STATISTIC(NumSunk,      "Number of machine instructions sunk");
 STATISTIC(NumSplit,     "Number of critical edges split");
@@ -311,7 +308,7 @@ MachineBasicBlock *MachineSinking::SplitCriticalEdge(MachineInstr *MI,
     return 0;
 
   // Avoid breaking back edge. From == To means backedge for single BB loop.
-  if (!SplitEdges || NumSplit == SplitLimit || FromBB == ToBB)
+  if (!SplitEdges || FromBB == ToBB)
     return 0;
 
   // Check for backedges of more "complex" loops.
@@ -561,8 +558,6 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
     // BreakPHIEdge is true if all the uses are in the successor MBB being
     // sunken into and they are all PHI nodes. In this case, machine-sink must
     // break the critical edge first.
-    if (NumSplit == SplitLimit)
-      return false;
     MachineBasicBlock *NewSucc = SplitCriticalEdge(MI, ParentBlock,
                                                    SuccToSinkTo, BreakPHIEdge);
     if (!NewSucc) {

llvm/test/CodeGen/Mips/2010-07-20-Select.ll

@@ -9,12 +9,12 @@ entry:
   volatile store i32 0, i32* %c, align 4
   %0 = volatile load i32* %a, align 4             ; <i32> [#uses=1]
   %1 = icmp eq i32 %0, 0                          ; <i1> [#uses=1]
-; CHECK: addiu $4, $zero, 3
+; CHECK: addiu $3, $zero, 0
   %iftmp.0.0 = select i1 %1, i32 3, i32 0         ; <i32> [#uses=1]
   %2 = volatile load i32* %c, align 4             ; <i32> [#uses=1]
   %3 = icmp eq i32 %2, 0                          ; <i1> [#uses=1]
-; CHECK: addu $4, $zero, $3
+; CHECK: addiu $3, $zero, 3
-; CHECK: addu $2, $5, $4
+; CHECK: addu $2, $5, $3
   %iftmp.2.0 = select i1 %3, i32 0, i32 5         ; <i32> [#uses=1]
   %4 = add nsw i32 %iftmp.2.0, %iftmp.0.0         ; <i32> [#uses=1]
   ret i32 %4

llvm/test/CodeGen/X86/compare-inf.ll

@@ -5,7 +5,7 @@
 
 ; CHECK: oeq_inff:
 ; CHECK: ucomiss
-; CHECK: jae
+; CHECK: jb
 define float @oeq_inff(float %x, float %y) nounwind readonly {
   %t0 = fcmp oeq float %x, 0x7FF0000000000000
   %t1 = select i1 %t0, float 1.0, float %y
@@ -14,7 +14,7 @@ define float @oeq_inff(float %x, float %y) nounwind readonly {
 
 ; CHECK: oeq_inf:
 ; CHECK: ucomisd
-; CHECK: jae
+; CHECK: jb
 define double @oeq_inf(double %x, double %y) nounwind readonly {
   %t0 = fcmp oeq double %x, 0x7FF0000000000000
   %t1 = select i1 %t0, double 1.0, double %y
@@ -23,7 +23,7 @@ define double @oeq_inf(double %x, double %y) nounwind readonly {
 
 ; CHECK: une_inff:
 ; CHECK: ucomiss
-; CHECK: jb
+; CHECK: jae
 define float @une_inff(float %x, float %y) nounwind readonly {
   %t0 = fcmp une float %x, 0x7FF0000000000000
   %t1 = select i1 %t0, float 1.0, float %y
@@ -32,7 +32,7 @@ define float @une_inff(float %x, float %y) nounwind readonly {
 
 ; CHECK: une_inf:
 ; CHECK: ucomisd
-; CHECK: jb
+; CHECK: jae
 define double @une_inf(double %x, double %y) nounwind readonly {
   %t0 = fcmp une double %x, 0x7FF0000000000000
   %t1 = select i1 %t0, double 1.0, double %y
@@ -41,7 +41,7 @@ define double @une_inf(double %x, double %y) nounwind readonly {
 
 ; CHECK: oeq_neg_inff:
 ; CHECK: ucomiss
-; CHECK: jae
+; CHECK: jb
 define float @oeq_neg_inff(float %x, float %y) nounwind readonly {
   %t0 = fcmp oeq float %x, 0xFFF0000000000000
   %t1 = select i1 %t0, float 1.0, float %y
@@ -50,7 +50,7 @@ define float @oeq_neg_inff(float %x, float %y) nounwind readonly {
 
 ; CHECK: oeq_neg_inf:
 ; CHECK: ucomisd
-; CHECK: jae
+; CHECK: jb
 define double @oeq_neg_inf(double %x, double %y) nounwind readonly {
   %t0 = fcmp oeq double %x, 0xFFF0000000000000
   %t1 = select i1 %t0, double 1.0, double %y
@@ -59,7 +59,7 @@ define double @oeq_neg_inf(double %x, double %y) nounwind readonly {
 
 ; CHECK: une_neg_inff:
 ; CHECK: ucomiss
-; CHECK: jb
+; CHECK: jae
 define float @une_neg_inff(float %x, float %y) nounwind readonly {
   %t0 = fcmp une float %x, 0xFFF0000000000000
   %t1 = select i1 %t0, float 1.0, float %y
@@ -68,7 +68,7 @@ define float @une_neg_inff(float %x, float %y) nounwind readonly {
 
 ; CHECK: une_neg_inf:
 ; CHECK: ucomisd
-; CHECK: jb
+; CHECK: jae
 define double @une_neg_inf(double %x, double %y) nounwind readonly {
   %t0 = fcmp une double %x, 0xFFF0000000000000
   %t1 = select i1 %t0, double 1.0, double %y

llvm/test/CodeGen/X86/sink-hoist.ll

@@ -6,10 +6,11 @@
 ; that it's conditionally evaluated.
 
 ; CHECK: foo:
-; CHECK:      divsd
 ; CHECK-NEXT: testb $1, %dil
-; CHECK-NEXT: jne
+; CHECK-NEXT: je
 ; CHECK-NEXT: divsd
+; CHECK-NEXT: ret
+; CHECK:      divsd
 
 define double @foo(double %x, double %y, i1 %c) nounwind {
   %a = fdiv double %x, 3.2
@@ -18,6 +19,24 @@ define double @foo(double %x, double %y, i1 %c) nounwind {
   ret double %z
 }
 
+; Make sure the critical edge is broken so the divsd is sunken below
+; the conditional branch.
+; rdar://8454886
+
+; CHECK: split:
+; CHECK-NEXT: testb $1, %dil
+; CHECK-NEXT: je
+; CHECK-NEXT: divsd
+; CHECK-NEXT: ret
+; CHECK:      movaps
+; CHECK-NEXT: ret
+define double @split(double %x, double %y, i1 %c) nounwind {
+  %a = fdiv double %x, 3.2
+  %z = select i1 %c, double %a, double %y
+  ret double %z
+}
+
+
 ; Hoist floating-point constant-pool loads out of loops.
 
 ; CHECK: bar:
@@ -68,9 +87,9 @@ return:
 ; Codegen should hoist and CSE these constants.
 
 ; CHECK: vv:
-; CHECK: LCPI2_0(%rip), %xmm0
+; CHECK: LCPI3_0(%rip), %xmm0
-; CHECK: LCPI2_1(%rip), %xmm1
+; CHECK: LCPI3_1(%rip), %xmm1
-; CHECK: LCPI2_2(%rip), %xmm2
+; CHECK: LCPI3_2(%rip), %xmm2
 ; CHECK: align
 ; CHECK-NOT: LCPI
 ; CHECK: ret

llvm/test/CodeGen/XCore/ashr.ll

@@ -50,9 +50,9 @@ define i32 @f3(i32 %a) {
 	ret i32 %2
 }
 ; CHECK: f3:
-; CHECK-NEXT: ashr r1, r0, 32
+; CHECK-NEXT: ashr r0, r0, 32
+; CHECK-NEXT: bf r0
 ; CHECK-NEXT: ldc r0, 10
-; CHECK-NEXT: bt r1
 ; CHECK: ldc r0, 17
 
 define i32 @f4(i32 %a) {
@@ -61,9 +61,9 @@ define i32 @f4(i32 %a) {
 	ret i32 %2
 }
 ; CHECK: f4:
-; CHECK-NEXT: ashr r1, r0, 32
+; CHECK-NEXT: ashr r0, r0, 32
+; CHECK-NEXT: bf r0
 ; CHECK-NEXT: ldc r0, 17
-; CHECK-NEXT: bt r1
 ; CHECK: ldc r0, 10
 
 define i32 @f5(i32 %a) {