diff options
author | Austin Clements <austin@google.com> | 2014-11-14 11:07:33 -0500 |
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committer | Austin Clements <austin@google.com> | 2014-11-14 11:07:33 -0500 |
commit | 9e0df37f450e937b3e2740da585eb7fe82aa3b2b (patch) | |
tree | 2337a6829b40fd1f31e33c5c7423cf66d17d3f94 /src/cmd/6g | |
parent | 9cabb766eb4acbe2c11ad0084659710919f40c0d (diff) | |
download | go-9e0df37f450e937b3e2740da585eb7fe82aa3b2b.tar.gz |
[dev.power64] 5g,6g,8g: synchronize documentation for regopt structures
I added several comments to the regopt-related structures when
porting it to 9g. Synchronize those comments back in to the
other compilers.
LGTM=rsc
R=rsc
CC=golang-codereviews
https://codereview.appspot.com/175720043
Diffstat (limited to 'src/cmd/6g')
-rw-r--r-- | src/cmd/6g/opt.h | 30 |
1 files changed, 23 insertions, 7 deletions
diff --git a/src/cmd/6g/opt.h b/src/cmd/6g/opt.h index 4c9bb89fc..08486a04a 100644 --- a/src/cmd/6g/opt.h +++ b/src/cmd/6g/opt.h @@ -75,12 +75,18 @@ struct Reg { Flow f; - Bits set; // variables written by this instruction. - Bits use1; // variables read by prog->from. - Bits use2; // variables read by prog->to. + Bits set; // regopt variables written by this instruction. + Bits use1; // regopt variables read by prog->from. + Bits use2; // regopt variables read by prog->to. + // refahead/refbehind are the regopt variables whose current + // value may be used in the following/preceding instructions + // up to a CALL (or the value is clobbered). Bits refbehind; Bits refahead; + // calahead/calbehind are similar, but for variables in + // instructions that are reachable after hitting at least one + // CALL. Bits calbehind; Bits calahead; Bits regdiff; @@ -93,6 +99,16 @@ struct Reg #define NRGN 600 /*c2go enum { NRGN = 600 }; */ + +// A Rgn represents a single regopt variable over a region of code +// where a register could potentially be dedicated to that variable. +// The code encompassed by a Rgn is defined by the flow graph, +// starting at enter, flood-filling forward while varno is refahead +// and backward while varno is refbehind, and following branches. A +// single variable may be represented by multiple disjoint Rgns and +// each Rgn may choose a different register for that variable. +// Registers are allocated to regions greedily in order of descending +// cost. struct Rgn { Reg* enter; @@ -165,8 +181,8 @@ typedef struct ProgInfo ProgInfo; struct ProgInfo { uint32 flags; // the bits below - uint32 reguse; // required registers used by this instruction - uint32 regset; // required registers set by this instruction + uint32 reguse; // registers implicitly used by this instruction + uint32 regset; // registers implicitly set by this instruction uint32 regindex; // registers used by addressing mode }; @@ -187,12 +203,12 @@ enum SizeF = 1<<7, // float aka float32 SizeD = 1<<8, // double aka float64 - // Left side: address taken, read, write. + // Left side (Prog.from): address taken, read, write. LeftAddr = 1<<9, LeftRead = 1<<10, LeftWrite = 1<<11, - // Right side: address taken, read, write. + // Right side (Prog.to): address taken, read, write. RightAddr = 1<<12, RightRead = 1<<13, RightWrite = 1<<14, |