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930aaa18e9
There is not an official documented ABI for frame pointers in Thumb2, but we should try to emit something which is useful. We use r7 as the frame pointer for Thumb code, which currently means that if a function needs to save a high register (r8-r11), it will get pushed to the stack between the frame pointer (r7) and link register (r14). This means that while a stack unwinder can follow the chain of frame pointers up the stack, it cannot know the offset to lr, so does not know which functions correspond to the stack frames. To fix this, we need to push the callee-saved registers in two batches, with the first push saving the low registers, fp and lr, and the second push saving the high registers. This is already implemented, but previously only used for iOS. This patch turns it on for all Thumb2 targets when frame pointers are required by the ABI, and the frame pointer is r7 (Windows uses r11, so this isn't a problem there). If frame pointer elimination is enabled we still emit a single push/pop even if we need a frame pointer for other reasons, to avoid increasing code size. We must also ensure that lr is pushed to the stack when using a frame pointer, so that we end up with a complete frame record. Situations that could cause this were rare, because we already push lr in most situations so that we can return using the pop instruction. Differential Revision: https://reviews.llvm.org/D23516 llvm-svn: 279506
101 lines
3.8 KiB
LLVM
101 lines
3.8 KiB
LLVM
; RUN: llc < %s -mtriple=thumbv7-apple-ios -mcpu=cortex-a9 -jump-table-density=40 | FileCheck %s
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; Test that ldmia_ret preserves implicit operands for return values.
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;
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; This CFG is reduced from a benchmark miscompile. With current
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; if-conversion heuristics, one of the return paths is if-converted
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; into sw.bb18 resulting in an ldmia_ret in the middle of the
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; block. The postra scheduler needs to know that the return implicitly
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; uses the return register, otherwise its antidep breaker scavenges
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; the register in order to hoist the constant load required to test
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; the switch.
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declare i32 @getint()
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declare i1 @getbool()
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declare void @foo(i32)
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declare i32 @bar(i32)
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define i32 @test(i32 %in1, i32 %in2) nounwind "no-frame-pointer-elim"="true" {
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entry:
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%call = tail call zeroext i1 @getbool() nounwind
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br i1 %call, label %sw.bb18, label %sw.bb2
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sw.bb2: ; preds = %entry
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%cmp = tail call zeroext i1 @getbool() nounwind
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br i1 %cmp, label %sw.epilog58, label %land.lhs.true
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land.lhs.true: ; preds = %sw.bb2
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%cmp13 = tail call zeroext i1 @getbool() nounwind
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br i1 %cmp13, label %if.then, label %sw.epilog58
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if.then: ; preds = %land.lhs.true
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tail call void @foo(i32 %in1) nounwind
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br label %sw.epilog58
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; load the return value
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; CHECK: movs [[RRET:r.]], #2
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; hoist the switch constant without clobbering RRET
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; CHECK: movw
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; CHECK-NOT: [[RRET]]
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; CHECK: , #63707
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; CHECK-NOT: [[RRET]]
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; CHECK: tst
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; If-convert the return
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; CHECK: it ne
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; Fold the CSR+return into a pop
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; CHECK: pop {r4, r5, r7, pc}
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sw.bb18:
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%call20 = tail call i32 @bar(i32 %in2) nounwind
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switch i32 %call20, label %sw.default56 [
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i32 168, label %sw.bb21
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i32 165, label %sw.bb21
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i32 261, label %sw.epilog58
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i32 188, label %sw.epilog58
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i32 187, label %sw.epilog58
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i32 186, label %sw.epilog58
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i32 185, label %sw.epilog58
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i32 184, label %sw.epilog58
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i32 175, label %sw.epilog58
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i32 174, label %sw.epilog58
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i32 173, label %sw.epilog58
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i32 172, label %sw.epilog58
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i32 171, label %sw.epilog58
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i32 167, label %sw.epilog58
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i32 166, label %sw.epilog58
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i32 164, label %sw.epilog58
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i32 163, label %sw.epilog58
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i32 161, label %sw.epilog58
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i32 160, label %sw.epilog58
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i32 -1, label %sw.bb33
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]
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sw.bb21: ; preds = %sw.bb18, %sw.bb18
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tail call void @foo(i32 %in2) nounwind
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%call28 = tail call i32 @getint() nounwind
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%tobool = icmp eq i32 %call28, 0
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br i1 %tobool, label %if.then29, label %sw.epilog58
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if.then29: ; preds = %sw.bb21
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tail call void @foo(i32 %in2) nounwind
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br label %sw.epilog58
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sw.bb33: ; preds = %sw.bb18
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%cmp42 = tail call zeroext i1 @getbool() nounwind
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br i1 %cmp42, label %sw.default56, label %land.lhs.true44
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land.lhs.true44: ; preds = %sw.bb33
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%call50 = tail call i32 @getint() nounwind
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%cmp51 = icmp slt i32 %call50, 0
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br i1 %cmp51, label %if.then53, label %sw.default56
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if.then53: ; preds = %land.lhs.true44
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tail call void @foo(i32 %in2) nounwind
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br label %sw.default56
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sw.default56: ; preds = %sw.bb33, %land.lhs.true44, %if.then53, %sw.bb18
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br label %sw.epilog58
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sw.epilog58:
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%retval.0 = phi i32 [ 4, %sw.default56 ], [ 2, %sw.bb21 ], [ 2, %if.then29 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb18 ], [ 2, %sw.bb2 ], [ 2, %land.lhs.true ], [ 2, %if.then ]
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ret i32 %retval.0
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}
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