From 4a544a79bd735967f1d33fe675ae4566dbd17813 Mon Sep 17 00:00:00 2001 From: Duncan Sands Date: Tue, 6 Sep 2011 13:37:06 +0000 Subject: Split the init.trampoline intrinsic, which currently combines GCC's init.trampoline and adjust.trampoline intrinsics, into two intrinsics like in GCC. While having one combined intrinsic is tempting, it is not natural because typically the trampoline initialization needs to be done in one function, and the result of adjust trampoline is needed in a different (nested) function. To get around this llvm-gcc hacks the nested function lowering code to insert an additional parent variable holding the adjust.trampoline result that can be accessed from the child function. Dragonegg doesn't have the luxury of tweaking GCC code, so it stored the result of adjust.trampoline in the memory GCC set aside for the trampoline itself (this is always available in the child function), and set up some new memory (using an alloca) to hold the trampoline. Unfortunately this breaks Go which allocates trampoline memory on the heap and wants to use it even after the parent has exited (!). Rather than doing even more hacks to get Go working, it seemed best to just use two intrinsics like in GCC. Patch mostly by Sanjoy Das. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139140 91177308-0d34-0410-b5e6-96231b3b80d8 --- docs/LangRef.html | 71 +++++++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 53 insertions(+), 18 deletions(-) (limited to 'docs') diff --git a/docs/LangRef.html b/docs/LangRef.html index 2b9ee24bf4..0ec08eb0a0 100644 --- a/docs/LangRef.html +++ b/docs/LangRef.html @@ -275,9 +275,10 @@
  • Debugger intrinsics
  • Exception Handling intrinsics
    • -
  • Trampoline Intrinsic +
  • Trampoline Intrinsics
    1. 'llvm.init.trampoline' Intrinsic
      2. +
    2. 'llvm.adjust.trampoline' Intrinsic
  • Atomic intrinsics @@ -7680,12 +7681,12 @@ LLVM.

    - Trampoline Intrinsic + Trampoline Intrinsics

    -

    This intrinsic makes it possible to excise one parameter, marked with +

    These intrinsics make it possible to excise one parameter, marked with the nest attribute, from a function. The result is a callable function pointer lacking the nest parameter - the caller does not need to @@ -7702,7 +7703,8 @@ LLVM.

       %tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86
   %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0
-  %p = call i8* @llvm.init.trampoline(i8* %tramp1, i8* bitcast (i32 (i8*, i32, i32)* @f to i8*), i8* %nval)
+  call i8* @llvm.init.trampoline(i8* %tramp1, i8* bitcast (i32 (i8*, i32, i32)* @f to i8*), i8* %nval)
+  %p = call i8* @llvm.adjust.trampoline(i8* %tramp1)
   %fp = bitcast i8* %p to i32 (i32, i32)*
    @@ -7720,12 +7722,12 @@ LLVM.

    Syntax:
    -  declare i8* @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>)
+  declare void @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>)
    Overview:
    -

    This fills the memory pointed to by tramp with code and returns a - function pointer suitable for executing it.

    +

    This fills the memory pointed to by tramp with executable code, + turning it into a trampoline.

    Arguments:

    The llvm.init.trampoline intrinsic takes three arguments, all @@ -7739,17 +7741,50 @@ LLVM.

    Semantics:

    The block of memory pointed to by tramp is filled with target - dependent code, turning it into a function. A pointer to this function is - returned, but needs to be bitcast to an appropriate - function pointer type before being called. The new function's signature - is the same as that of func with any arguments marked with - the nest attribute removed. At most one such nest argument - is allowed, and it must be of pointer type. Calling the new function is - equivalent to calling func with the same argument list, but - with nval used for the missing nest argument. If, after - calling llvm.init.trampoline, the memory pointed to - by tramp is modified, then the effect of any later call to the - returned function pointer is undefined.

    + dependent code, turning it into a function. Then tramp needs to be + passed to llvm.adjust.trampoline to get a pointer + which can be bitcast (to a new function) and + called. The new function's signature is the same as that of + func with any arguments marked with the nest attribute + removed. At most one such nest argument is allowed, and it must be of + pointer type. Calling the new function is equivalent to calling func + with the same argument list, but with nval used for the missing + nest argument. If, after calling llvm.init.trampoline, the + memory pointed to by tramp is modified, then the effect of any later call + to the returned function pointer is undefined.

    +
    + + +

    + + 'llvm.adjust.trampoline' Intrinsic + +

    + +
    + +
    Syntax:
    +
    +  declare i8* @llvm.adjust.trampoline(i8* <tramp>)
+
    + +
    Overview:
    +

    This performs any required machine-specific adjustment to the address of a + trampoline (passed as tramp).

    + +
    Arguments:
    +

    tramp must point to a block of memory which already has trampoline code + filled in by a previous call to llvm.init.trampoline + .

    + +
    Semantics:
    +

    On some architectures the address of the code to be executed needs to be + different to the address where the trampoline is actually stored. This + intrinsic returns the executable address corresponding to tramp + after performing the required machine specific adjustments. + The pointer returned can then be bitcast and + executed. +

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