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%AConst = constant int 123
implementation
; A SetCC whose result is used should produce instructions to
; compute the boolean value in a register. One whose result
; is unused will only generate the condition code but not
; the boolean result.
;
void "unusedBool"(int * %x, int * %y)
begin
; <label>:0 ; [#uses=0]
seteq int * %x, %y ; <bool>:0 [#uses=1]
not bool %0 ; <bool>:1 [#uses=0]
setne int * %x, %y ; <bool>:2 [#uses=0]
ret void
end
; A constant argument to a Phi produces a Cast instruction in the
; corresponding predecessor basic block. This checks a few things:
; -- phi arguments coming from the bottom of the same basic block
; (they should not be forward substituted in the machine code!)
; -- code generation for casts of various types
; -- use of immediate fields for integral constants of different sizes
; -- branch on a constant condition
;
void "mergeConstants"(int * %x, int * %y)
begin
; <label>:0
br label %Top
Top:
phi int [ 0, %0 ], [ 1, %Top ], [ 524288, %Next ]
phi float [ 0.0, %0 ], [ 1.0, %Top ], [ 2.0, %Next ]
phi double [ 0.5, %0 ], [ 1.5, %Top ], [ 2.5, %Next ]
phi bool [ true, %0 ], [ false,%Top ], [ true, %Next ]
br bool true, label %Top, label %Next
Next:
br label %Top
end
; A constant argument to a cast used only once should be forward substituted
; and loaded where needed, which happens is:
; -- User of cast has no immediate field
; -- User of cast has immediate field but constant is too large to fit
; or constant is not resolved until later (e.g., global address)
; -- User of cast uses it as a call arg. or return value so it is an implicit
; use but has to be loaded into a virtual register so that the reg.
; allocator can allocate the appropriate phys. reg. for it
;
int* "castconst"(float)
begin
%castbig = cast ulong 99999999 to int
%castsmall = cast ulong 1 to int
%usebig = add int %castbig, %castsmall
%castglob = cast int* %AConst to long*
%dummyl = load long* %castglob
%castnull = cast ulong 0 to int*
ret int* %castnull
end
; Test branch-on-comparison-with-zero, in two ways:
; 1. can be folded
; 2. cannot be folded because result of comparison is used twice
;
void "testbool"(int, int) ; Def %0, %1
const int 0 ; Def 2
const int -4 ; Def 3
begin
add int %0, %1 ; Def 4
sub int %4, %3 ; Def 5
setle int %5, %2 ; Def 0 - bool plane
br bool %0, label %retlbl, label %loop
loop:
add int %0, %1 ; Def 6
sub int %4, %3 ; Def 7
setle int %7, %2 ; Def 1 - bool
not bool %1 ; Def 2 - bool. first use of bool %1
br bool %1, label %loop, label %0 ; second use of bool %1
retlbl:
ret void
end
; Test branch on floating point comparison
;
void "testfloatbool"(float %x, float %y) ; Def %0, %1 - float
begin
%p = add float %x, %y ; Def 2 - float
%z = sub float %x, %y ; Def 3 - float
%b = setle float %p, %z ; Def 0 - bool
%c = not bool %b ; Def 1 - bool
br bool %b, label %0, label %goon
goon:
ret void
end
; Test cases where an LLVM instruction requires no machine
; instructions (e.g., cast int* to long). But there are 2 cases:
; 1. If the result register has only a single use and the use is in the
; same basic block, the operand will be copy-propagated during
; instruction selection.
; 2. If the result register has multiple uses or is in a different
; basic block, it cannot (or will not) be copy propagated during
; instruction selection. It will generate a
; copy instruction (add-with-0), but this copy should get coalesced
; away by the register allocator.
;
int "checkForward"(int %N, int* %A)
begin
bb2: ;;<label>
%reg114 = shl int %N, ubyte 2 ;;
%cast115 = cast int %reg114 to int* ;; reg114 will be propagated
%reg116 = add int* %A, %cast115 ;;
%reg118 = load int* %reg116 ;;
%cast117 = cast int %reg118 to long ;; reg118 will be copied 'cos
%reg159 = add long 1234567, %cast117 ;; cast117 has 2 uses, here
%reg160 = add long 7654321, %cast117 ;; and here.
ret void
end
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