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