diff options
| -rw-r--r-- | lib/CodeGen/MachineBlockPlacement.cpp | 5 | ||||
| -rw-r--r-- | test/CodeGen/X86/block-placement.ll | 41 |
2 files changed, 45 insertions, 1 deletions
diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp index 4cbc94e0b7..0d15e8a726 100644 --- a/lib/CodeGen/MachineBlockPlacement.cpp +++ b/lib/CodeGen/MachineBlockPlacement.cpp @@ -488,7 +488,10 @@ MachineBasicBlock *MachineBlockPlacement::getFirstUnplacedBlock( continue; if (BlockToChain[I] != &PlacedChain) { PrevUnplacedBlockIt = I; - return I; + // Now select the head of the chain to which the unplaced block belongs + // as the block to place. This will force the entire chain to be placed, + // and satisfies the requirements of merging chains. + return *BlockToChain[I]->begin(); } } return 0; diff --git a/test/CodeGen/X86/block-placement.ll b/test/CodeGen/X86/block-placement.ll index 8a8bf1345e..05d6f8138f 100644 --- a/test/CodeGen/X86/block-placement.ll +++ b/test/CodeGen/X86/block-placement.ll @@ -503,3 +503,44 @@ lpad: loop: br label %loop } + +define void @test_unnatural_cfg_backwards_inner_loop() { +; Test that when we encounter an unnatural CFG structure after having formed +; a chain for an inner loop which happened to be laid out backwards we don't +; attempt to merge onto the wrong end of the inner loop just because we find it +; first. This was reduced from a crasher in GCC's single source. +; +; CHECK: test_unnatural_cfg_backwards_inner_loop +; CHECK: %entry +; CHECK: %body +; CHECK: %loop1 +; CHECK: %loop2b +; CHECK: %loop2a + +entry: + br i1 undef, label %loop2a, label %body + +body: + br label %loop2a + +loop1: + %next.load = load i32** undef + br i1 %comp.a, label %loop2a, label %loop2b + +loop2a: + %var = phi i32* [ null, %entry ], [ null, %body ], [ %next.phi, %loop1 ] + %next.var = phi i32* [ null, %entry ], [ undef, %body ], [ %next.load, %loop1 ] + %comp.a = icmp eq i32* %var, null + br label %loop3 + +loop2b: + %gep = getelementptr inbounds i32* %var.phi, i32 0 + %next.ptr = bitcast i32* %gep to i32** + store i32* %next.phi, i32** %next.ptr + br label %loop3 + +loop3: + %var.phi = phi i32* [ %next.phi, %loop2b ], [ %var, %loop2a ] + %next.phi = phi i32* [ %next.load, %loop2b ], [ %next.var, %loop2a ] + br label %loop1 +} |