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llvm-mirror/test/CodeGen/Mips/lazy-binding.ll
Akira Hatanaka e5351a10fe [mips] Make sure loads from lazy-binding entries do not get CSE'd or hoisted out
of loops.

Previously, two consecutive calls to function "func" would result in the
following sequence of instructions:

1. load $16, %got(func)($gp) // load address of lazy-binding stub.
2. move $25, $16
3. jalr $25                  // jump to lazy-binding stub.
4. nop
5. move $25, $16
6. jalr $25                  // jump to lazy-binding stub again.

With this patch, the second call directly jumps to func's address, bypassing
the lazy-binding resolution routine:

1. load $25, %got(func)($gp) // load address of lazy-binding stub.
2. jalr $25                  // jump to lazy-binding stub.
3. nop
4. load $25, %got(func)($gp) // load resolved address of func.
5. jalr $25                  // directly jump to func.

llvm-svn: 191591
2013-09-28 00:12:32 +00:00

42 lines
1022 B
LLVM

; RUN: llc -march=mipsel < %s | FileCheck %s
; CHECK-LABEL: foo6:
; CHECK: %while.body
; CHECK: lw $25, %call16(foo2)(${{[0-9]+}})
; CHECK: jalr $25
; CHECK: %while.end
define void @foo6(i32 %n) {
entry:
%tobool1 = icmp eq i32 %n, 0
br i1 %tobool1, label %while.end, label %while.body
while.body: ; preds = %entry, %while.body
%n.addr.02 = phi i32 [ %dec, %while.body ], [ %n, %entry ]
%dec = add nsw i32 %n.addr.02, -1
tail call void @foo2()
%tobool = icmp eq i32 %dec, 0
br i1 %tobool, label %while.end, label %while.body
while.end: ; preds = %while.body, %entry
ret void
}
declare void @foo2()
; CHECK-LABEL: foo1:
; CHECK: lw $25, %call16(foo2)(${{[0-9]+}})
; CHECK: jalr $25
; CHECK: lw $25, %call16(foo2)(${{[0-9]+}})
; CHECK: jalr $25
; CHECK: lw $25, %call16(foo2)(${{[0-9]+}})
; CHECK: jalr $25
define void @foo1() {
entry:
tail call void @foo2()
tail call void @foo2()
tail call void @foo2()
ret void
}